Canon Scanner – Unable to open TWAIN source

I have a Canon CanoScan 4400F Scanner and the other day I was unable to get it to work.  I use the Canon software CanoScan Toolbox to operate the scanner and when trying to scan I was getting the following error message:


CanoScan Toolbox
Unable to open TWAIN source
Please check connection
Then re-start Toolbox

Searching the Internet for this problem turned up several people having the same problem and several solutions which looked like they may or may not work.  One of the recommended solutions was to make sure a certain folder path is in your PATH environment variable.  As it turned out this was the problem, so here is how to add that path back into your environment variables.

First, determine the correct path to add into the PATH environment variable.  Look in C:\Windows\twain_32 and there should one other folder in there.  In my case it was  named CNQ4803.


This is the path that is needed to be added into the PATH environment variable.



Now, follow these instructions to get to the dialog to modify the PATH environment variable.

Control Panel > System > and then choose Advanced System Settings in the left hand column.


This will bring up the System Properties dialog (it should already be on the Advanced tab).


At the bottom of this dialog is an Environment Variables button.  Clicking this button will bring up the Environment Variables dialog.


In the bottom panel, scroll until you find the variable named Path.  Select this one and then hit the Edit… button to bring up the Edit System Variable dialog.


In the Variable value text box, scroll all the way to the right and then add in the path C:\Windows\twain_32\CNQ4803 that was determined earlier.  Make sure to separate this value with a preceding semi-colon.  And also be careful not to make any other changes to this value.

Now OK your way out of all of the dialogs and CanoScan Toolbox will now work as expected.


Published 02 November 2009 11:49 PM by Jeff Widmer


# Jon Davis said on 04 November, 2009 12:42 AM

Jeff: I want to thank you SO much for this information. I've had my 4400F about 2 years; today was the first time I had ever run into this 'twain' problem. For some reason, it has, many times in the past, 'lost' something in the CanoScan Toolbox. That only required uninstalling and reinstalling the Toolbox software. Anyway, I followed your instructions and all is fine now. Thanks again.

# Silvio said on 30 November, 2009 10:36 AM

jeff - many thanks for the are a true gentleman

# Jackie said on 08 December, 2009 12:42 AM

Jeff - many thanks for your time and help.

Perfect solution.

# Denton said on 03 January, 2010 10:12 PM

Me Too!

My canon LiDE 70 has been working fine for years.  I recently installed Roxio Creator 2010 and I believe it is what munged my path. This fixed worked when reinstalling the drivers and CanoScan did not.  Many Thanks!

# Jarryd Semmens said on 17 January, 2010 07:58 AM

Fixed my scanner after reading this. Thankyou.

# Sparky said on 26 January, 2010 09:33 PM

I've also started running Win 7 64-bit and this scanner simply will not work with it.  This fix did not help. I've been working on it for days and am just going to give it away to a friend and buy another scanner.  Anything but a Canon.

# RW said on 09 February, 2010 03:25 PM

Jeff, this worked!  I spent the whole morning checking blogs and the Canon site.  Thanks so much for sharing ...

# Dhanunjay said on 22 March, 2010 02:14 PM

Thanks for your help it resolved my problem.

# Ronny said on 23 March, 2010 09:46 AM

Big thanks. I was about to do some reinstall and was saved by this post!

# Lone Wolf said on 31 March, 2010 10:19 AM

Mucho Gracias Senor Jeff!  apparently an Oracle XE  installations messed my path.

God Bless!

# thanks said on 02 April, 2010 04:05 AM

veeeeeeeeeery thanks

# Chuck said on 21 April, 2010 04:46 PM

Jeff!!  Thanks a bunch!!!!!

# Nicole Hamilton said on 10 May, 2010 01:47 AM

When Canon's miscreant CanoScan app suddenly stopped working with my 8400F scanner, I tried everything else I could think of but nothing worked.  Rebooting, system restoring, reinstalling the app, reinstalling just the driver, running in compatibility mode, yada, yada.  Nothing worked.

Then I discovered this page.  This worked.  Thank you!

# David said on 18 May, 2010 07:49 PM

Thanks for the solution - this did the trick!

# Jack said on 02 June, 2010 10:24 AM

This method  works on my CanScan Lide 30. Thanks!

# Mattia said on 04 July, 2010 03:47 PM

you are simply great!

# Keith McCombe said on 11 August, 2010 05:13 AM

Thanks Jeff - fixed my cannon 4200F which stopped working (unable to open TWAIN source) One of my recently installed apps. must have corrupted the PATH variable. Now working OK. Thanks again.

# Ajay Sharma said on 11 August, 2010 03:12 PM

Thank you Jeff! This fixed the issue with my canoscan 656u not working on Windows 2003. I had to use Windows 2000 drivers for it, but that's besides the point. Putting the Twain_32 folder in Path variable was the solution for me.

# Jeffrey Crawford said on 15 August, 2010 12:33 AM

I tried the above solution for my FB630u Canoscan on a Vista system.  It worked like a charm.  Thank you so much.

# Marco said on 15 August, 2010 04:11 PM

Thank you very much!

# BruceL said on 17 August, 2010 05:55 PM

Thanks very much, Jeff!  Also works with the 4200F on Windows 32-bit Vista Home Edition.

# Fredrik said on 25 September, 2010 02:49 AM

Thank you so much! Finally got the scanner working!

# Ross said on 29 September, 2010 08:25 PM

Absolute legend!!  Why this isn't simply found when updating drivers etc on the Canon site.

# Nikos said on 05 October, 2010 01:13 PM

Thanks a lot! Worked fine for LIDE 35 on Vista Ultimate 32bit.

# Chris said on 11 October, 2010 05:55 AM

Brilliant.  This fixed it for Windows 7 64 Bit.

Looks like Acronis backup software install messed up the path variable.

Due to the wide range of apps that seem to mess up the path settings I wonder if its a windows bug or if the canon install doesn't format it correctly in the first perhaps it needs a trailing ;

# Ashleigh said on 24 October, 2010 07:36 PM

Thanks a million! Solved my issue--thought I was going to have to finally upgrade scanners but now I can hold out longer.

# Pete said on 01 November, 2010 08:42 AM

Unfortunately, it didn't work for me... It tells me that "Release the lock switch, detach I/F cable and reconnect. Scanner driver will be closed." than it gives the TWAIN error. I read something about a black-and-white bar near the front controls which the scanner uses for aligning, and that the problem might be that it is warped somehow. Anyone knows something about this problem, or preferably, to fix it? I have a lide 25...

# Jan said on 17 November, 2010 05:08 PM

Thanks, for advice. :-)

# jesse wu said on 10 December, 2010 08:53 PM


fix my problem. Thanks

# Howard Fong 914 Porsche said on 05 January, 2011 06:38 AM

I feel unlucky. This did not work for me after upgrading some Intel WIFI drivers. The "path" details you mention arleady have some Intel thing in it so I added what you said seperated by a semicolon but still get the error message. what do do next? Thanks in advanced. Am using W764-bit. Should I use 64 instead of 32 in the text? Also, I have the LIDE25

# Howard Fong 914 Porsche said on 05 January, 2011 06:44 AM

OK, I'm bad. Want to update for future readers with same specifics (W7 64bit and LIDE 25). I had input the wrong LIDE model in my path edit. Left it at 32 for 32 bit and the scanner works. Whooo hooo! Hooray!

P.S., should I change to 64 intead of 32 in the text edit? Are the drivers really 64 bit? I installed the latest complete software package from the Cannon U.S. support site. The description says its for W7 64 but if one tries downloading the driver serprately it is only for 32 bit. Can Cannon be any more bad at support?

# David said on 16 January, 2011 02:03 PM

Did not work.  I'm still getting

"Release the Lock Switch, Detach the USB

cable, and Reconnect. The scanner driver will close"


"Unable to open TWAIN source. Please check the connection and start again"

This is on a LiDE 20 scanner

# Elbert Waller said on 30 January, 2011 09:24 AM

Thanks! Did work for me.

# Brian Savvas said on 03 February, 2011 12:36 AM

Thanks, it worked for me on a Canoscan LiDE25 after two days lost and Canon unable to help.

# Ken said on 09 February, 2011 07:35 AM

This is simply awesome. It works fantastic for my CanoScanLide25. Thanks a lot. I have been figuring out for the whole night.


# Ray Jones said on 14 February, 2011 04:49 PM

I tried this and it did not work.  I have been using the scanner for several years and have been able to reload it and use it successfully on a new Vista system.  Suddenly it stopped working.

The existing path appears quite strange to me and is as follows:

C:\Program Files\CommonFiles\ArcSoft\Bin;%SystemRoot%system32;%SystemRoot%;%SystemRoot%\System32\Wbem

ArcSoft is the photo software that I am working with.  But it won't work directly from the CanoScan Toolbox either.

I tried adding C:\Windows\TWAIN_32\CNQL30 directly after adding the semi-colon and then by adding a semi-colon and a backslash.  Neither worked.

Any other ideas?

Thanks for helping

# Scottt said on 19 February, 2011 01:56 AM

Thanks you so much for the tip.  My Canon LiDE 500F worked fine for years and one day I got this TWAIN error.  I tried uninstall a few times but it still didn't fix the problem until I found the solution on your site.  Good sharing!

# Darth Continent said on 03 March, 2011 11:03 PM

Thanks, this worked for my Canon LIDE 25!

Windows 7 Ultimate is my OS, and although I couldn't get Canon's own CanoScan Toolbox to work, I was able to get Windows 7's scanner driver operational with the above. The only difference was my TWAIN file path, I had to add this to my PATH setting:


After a reboot, my CanoScan LIDE 25 is working once more.

# vichet said on 13 March, 2011 09:46 AM

thanks you very much. I tried many method from many forum but cannot make my scanner work. But this time, the problem solved.

# Eve said on 15 March, 2011 09:34 PM

Help, I think I messed up the entire path line accidentally. How can I fix it? Do you have the entire text that should be there??

# Walter said on 31 March, 2011 12:15 PM


Thanks so much for posting this fix.  It was not obvious why the scanner would have failed after working for a couple of years.  I just wonder, how did you find this out?

# Rowan said on 20 April, 2011 03:20 PM

Many thanks Jeff,  

My daughter in Australial mailed me with the problem, I contacted my son (the wizz kid) in Sweden & he sent her the link. the fix is  done and now I get the scanned documentation I needed.

# yulia said on 21 April, 2011 11:17 AM

thanks a lot!

i can't find any infomation about the problem in Chinese! So i arrive at  here through Google, and it works! 太好了!

# Warren said on 23 April, 2011 11:53 AM

Thanks - you saved me from buying a new scanner!

# Tarun said on 24 April, 2011 09:43 PM

Thanks a lot. I've had this scanner for a couple of years - and encountered this problem for the first time today (of course, when I needed it to work urgently). Luckily, I ran across your solution first and am back up and running now.

Once again, Thanks a million!

# Sune said on 02 May, 2011 04:47 AM

Thanks a lot from Copenhagen, Denmark

# Rob Butler said on 03 May, 2011 04:52 PM

Thanks for your instructions - got my Canon scanner working a treat!

# Sreedhar said on 14 May, 2011 09:08 AM

Thanks for the information so much...

# David said on 15 May, 2011 05:16 PM

Fantastic, worked like a charm on my Windows 2003 Server 64-bit. Like with many others, this problem just happened recently with the CanoScan working great before. In any event, the solution worked super well for me. Thanks a ton!

# Tim said on 16 May, 2011 02:04 PM

Thanks Jeff, luckly found this page quickly LIDE70 fixed in no time on both XP and Vista computers!

# Rob said on 16 May, 2011 02:45 PM

Jeff, you Sir, are a Gentleman and a Scholar, a million thanks, excellent walkthrough and worked an absolute treat, once again many thanks.

# Joe said on 19 May, 2011 01:41 PM

Wow! Brlliant fix! Thank you!

# MANOLIS XANIA said on 26 May, 2011 05:43 AM

YOU ARE THE BEST!!!!!!!! THANKS WORKING FINE NOW!!!!!!!!!!!!!!!!!!!!!!!

# Gary Davis said on 29 May, 2011 11:24 AM

Thanks, it worked for me. Not sure how it worked over the previous years! I updated the drivers from the Canon site but that did not help. The Path addition was the needed fix.

Gary Davis

# Rob Callaghan said on 31 May, 2011 09:22 AM

I have just had this problem. File CNQ4803 is in the C:\Windows\twain_32 folder.

I just tried to edit the path, but only got as far as Control Panel and System and Security.

I have no advanced settings tab in my system and security menu.

Re-installing the programme does not help as I continue to get the same message.

# Tresy Kilbourne said on 04 June, 2011 11:15 PM

Man, you are a lifesaver. My 4200F stopped working after upgrading to Win 7 SP1. I was on the verge of throwing out the scanner and buying a new one. Thanks.

# morgan said on 11 June, 2011 04:28 PM

Canon driver self-installs in c:\canon not c:\windows\twain.  I copied it to \windows\twain and pathed it . . . nothing different

# Tamas said on 17 June, 2011 05:45 AM

Thanks so much!

I have a Canon Lide 25, my path to twain is:


After putting it into path variable scanner get working again!

# Josh said on 17 June, 2011 04:57 PM

This path worked great with my CanoScan 4200F: C:\Windows\twain_32\CNQ4200


# Anthony L said on 17 June, 2011 10:50 PM

Running Vista Home Premium. My CanoScan N1220U, about 10 years old now, is only used it a few times a year. Like everyone else has experienced, it just stopped working! Added the folder to the system path and it started working again. Thanks!!!

I can't imagine that something just took it out of the path. I doubt it was ever there to begin with. Must have been some system configuration change or other service pack that mucked up Twain, but what do I know. Regardless I'm glad its working now, saved me a trip to Staples. Thanks a million!

# elliphant said on 28 June, 2011 03:47 PM

Apologies if this is redundant, I didn't read through the entire thread. Win7x64: use Canoscan Toolbox v4.9, not v5.0. For some reason the newer one doesn't work, but the older one does (5.0 might work on 32-bit, don't know). Install the driver first (SetupSG.exe) (look for 8400fvst6410231a_64en [32en for 32-bit, I would think]) then install the Toolbox (csbwin4932en). You might have to use Jeff's path variable trick; I did that before all the rest and I didn't go back and test without it, so YMMV. Once everything is done you will need to reboot before everything will work. A good tool for testing and troubleshooting is to download Irfanview, which has Twain and scanning tools under the File menu. Enjoy!

# elliphant said on 28 June, 2011 03:52 PM

Geez, forgot to say that I'm using an 8400f - procedure might work for other older models too.

# Will said on 30 June, 2011 05:10 AM

I just want to say thank you.

My canoscan lide 70 works like charm.

# Oscar said on 30 June, 2011 10:18 PM

I have a canoscan 4200F and it worked before I installed W7 (x64) SP1 but not since. I tried this and it doesn't work.

# Rob said on 04 July, 2011 11:30 PM

Hi Jeff. Thanks very much. I have spent hours with unistalling and reinstalling the Canon drivers and software to solve this problem which made no impact. I tried your solution on my XP system and it worked perfectly. Thanks again.

# Maria said on 06 July, 2011 06:12 AM

Thank you so much!!!

My Canoscan Lide 60 is working again and your instruction made it fast and simple. Great!

# Anton Staykov said on 06 July, 2011 06:40 PM

Great helpful post!

# Selton BFK said on 08 July, 2011 02:47 PM

Muchas gracias! me ahorraste mucho trabajo!

# Jakub said on 11 July, 2011 04:02 PM

damn. this left me two months without home scanner after a reinstall to Win 7. Thanks a lot for the trick.

Why can't the installer add the path itself. Or why is it necessary to have it in the PATH variable in the first place.

But I gess we can be lucky Canon provides 64 bit drivers for such old products.

# Kurt Johnson said on 27 July, 2011 05:50 PM

Another satisfied customer.

PATH add was my answer for an LIDE35 on Windows 7 (32-bit).

Thanks, Jeff!

# JB Leep said on 29 July, 2011 05:18 PM

I have been doing this sort of stuff a long time, and when I come across someone who gives such a precise and effective answer, I find it truly awesome.  thanks so much for your efforts.

# Marek from Czech said on 30 July, 2011 08:25 AM

Thanks for your help!

# Melissa said on 31 July, 2011 11:45 PM

Thank you, this work fantastically! I can stop swearing at my scanner now...

# Vladimir said on 04 August, 2011 08:09 AM

Thank you, it worked for me. Only the puzzle is why the problem appeared. It worked for more than one year without any problem.

# Joseph said on 07 August, 2011 01:17 PM

Hi Jeff,

Thank you very much for the clear and concise instructions, it helped to fix the error quickly.



# Boyd said on 15 August, 2011 11:26 AM

Thanks mate, got my Canon LiDE 25 working again.

# heppa said on 23 August, 2011 03:01 PM

Thanks! This fixed also my Canon F4200 with Windows XP with same problem.

# AB said on 26 August, 2011 06:27 PM

Thank you so much!

# Green Forest said on 03 September, 2011 10:32 PM

Thank you so so much! By your advice, I've fixed my Canon LiDE 60 with Windows 7 with the same problem. Now I am enjoying the great performance of my scanner again!

I'm so grateful to you!


# Gianfranco said on 11 September, 2011 07:30 AM

thank you very much

# Michelle said on 13 September, 2011 10:06 AM

I used your info to fix my old Canon LiDe scanner. It was great to find this solution on the internet.  It really works!  Thanks for keeping this info out there for us to find.  

# neeta said on 15 September, 2011 04:49 AM

hi I have a Canoscan 5200F and I get the same message about TWAIN source. I did everything as indicated above but the toolbox still does not function! so what can I do now??

# Magnus said on 15 September, 2011 08:58 AM

Awesome! Finally I can scan with my FB630U with Vista and Picasa.

thanks for the info!

# BAN ANG said on 15 September, 2011 04:02 PM

Thank you very much for the info. I was going to buy a new scanner. Imagine that.

You just saved me some bucks

# RJ said on 16 September, 2011 10:39 AM

Thanks for the blog entry. Solved my problem.

# Jonathan Ezor said on 21 September, 2011 11:25 PM

As with the others, thanks so much! {Jonathan}

# Wolfgang said on 22 September, 2011 12:44 PM

Cool, thanks a lot. Took me a hour to get the Scanner running on x64.

# Eric said on 24 September, 2011 09:25 PM

Solved on win7 x64!

# Jan Bart (De Bilt in the Netherlands) said on 28 September, 2011 04:05 PM

Thanks Jeff for the information regarding the "path". Unfortunately it did not work but together with the comment from Elliphant on June 28: use canoscan v4.9 in stead of v5.0 I got my scanner 8400f working again.

# Piotr said on 29 September, 2011 10:42 AM

Jeff - Now it works ! :) THANK YOU

CanoScan 4200F & Win7 x64

# Jackie said on 01 October, 2011 12:46 PM

Hey there, this didn't work for me unfortunately, I have a Canon N670U and it suddenly stopped working about a month ago saying its unable to open TWAIN source, do you have any other ideas?  Thanks, Jackie

# Tibor said on 02 October, 2011 05:17 AM

Hi Jeff,

Thank you so much. This helped me with CanoScan 8400F.



# Bernhard said on 10 October, 2011 09:04 AM

I was unlucky - didn't work - still: many thanks.

# Jeremy said on 13 October, 2011 07:47 AM

Hi Jeff,

Thanks! Quick easy fix! Canoscan LiDE 60

# Matrix said on 14 October, 2011 07:52 PM

Big thanks Jeff! CanoScan 4400F. Used to work fine for years. Suddenly stop working today. Don't know how the environment variable got changed. Windows update maybe?

# Richard Collette said on 16 October, 2011 07:32 PM

I wish I had found this years ago.  Finally my Canoscan 8400F works and with both Canoscan Toolbox and Picasa as well.

# Aleksandar said on 22 October, 2011 09:30 AM

You are magnificent! Working perfectly now.

# Cas said on 26 October, 2011 02:38 AM

Thanks Jeff - it didn't fix my CanoScan D1250U2F problem but your instructions were really easy to follow and made me feel less frustrated nevertheless!

# JOG said on 02 November, 2011 09:28 AM

Thanks Jeff it fixed the problem on my CanoScan LiDE 600F



# Canonlide25 said on 06 November, 2011 07:47 AM

YES IS FIXED, this works on Windows 7, no in XP

En XP no se arreglo nada, pero en Windows7 si funciono


Thanks a lot!!!

# CheekyKelz said on 06 November, 2011 07:53 AM

Hiya Jeff, I was wondering if you could post that entire pathway plz because I accidentally deleted the pathway instead of just adding to it. I went to press the arrow on my laptop and pressed wrong button grrrrrrrr, could you help plz thanks

# Jeff Widmer said on 07 November, 2011 05:06 AM

Hi CheekyKelz,

Unfortunately the PATH variable is specific to your computer; as new applications are installed, new paths are added.  At a minimum it will include this:



# Dave Sellers said on 16 November, 2011 12:15 PM

Yep, worked for me too! Cheers Jeff.

# Kevin Rothwell said on 16 November, 2011 12:53 PM

Thanks Jeff! Your kindness in posting this solution is STILL helping people out! After installing a new Canon multi-function printer, my old Cannon 9950F scanner stopped working with the error described. (It's got a long scanning bed, so I want to keep it.) It now works again after following your instructions. Thanks again!!

# Nate said on 16 November, 2011 03:55 PM

Thanks! That fixed it for me too!

# Nathan said on 17 November, 2011 10:55 AM

I could Kiss you! you absolute legend!

# Henny said on 24 November, 2011 01:58 PM

No luck for me, but awesome this has worked for so many people. I am trying to setup CanoScan LIDE 50 on Windows Vista Home 64 bit. Very annoyed at Canon for being so unenvironmental - imagine all the scanners that just go to landfill because people can't figure this stuff out.

# Jovandeka said on 25 November, 2011 03:11 PM

Thanks for your help!

Jeff for President!!!

# Jake said on 02 December, 2011 05:32 PM

You just saved my bacon.

# Otto said on 06 December, 2011 10:57 AM

Great help. Thank u so much

# man in motion said on 19 December, 2011 03:18 AM

Thank you very very much! Made my day!

# Josef said on 28 December, 2011 10:01 AM

Thanks so much,

after reading so much different threads and spendings HOURS of other solutions (including a complete Factory re-set),

this worked liked nothing ...

# Alexander Avidan said on 29 December, 2011 01:43 AM

Excellent!!!!!!!!! Worked great.

Thanks a lot.

# Ehoa said on 29 December, 2011 12:16 PM

Many thanks! Don't know how this PATH got lost...

# Sebastian said on 03 January, 2012 11:27 AM

Thanks Jeff, our Lide 60 is back working again on Windows 7!

# Rick said on 04 January, 2012 05:33 PM

I have a Canon CanoScan 5200f

I Did exactly as you instructed...I also double checked and did a restart... but unfortunatley the exact same problem persists...'unable to select TWAIN source'

I have Windows7 64bit...i first downloaded and installed driver from CNET then found the tool box exe elsewhere and installed in 2-steps...perhaps this is the issue as when using the toolbox it always asks to select source after which the issue arises...any thoughts on this one???



# Jeff Widmer said on 04 January, 2012 09:48 PM

Hi Rick,

Try downloading the latest version of the Windows 7 64-bit Canon software from Canon's website:


# Francesco said on 05 January, 2012 06:36 AM

Thanks for the help, saved my day with my CanoScan 5200F

# Haymo said on 05 January, 2012 11:43 PM

thank you so much for this!

# Aaro from Finland said on 06 January, 2012 01:56 PM

Thanks a lot Jeff

This was great and solved my problem immediately

# Long Zheng said on 12 January, 2012 12:38 AM

Thanks. This fixed the problem I was having with my Caonn MP800 and the MP Navigator software as well. It would just give me a "Scan failed" every time.

I eventually figured out it was a TWAIN problem by looking at %temp%\twain.log which had "CloseServer - Why Can't We Find The Thunker Window?" but didn't know how to fix it.

Lo and behlold, I added the C:\Windows\twain_32\MP800 directory to my PATH and it works again!

# Jeff Widmer said on 12 January, 2012 06:05 AM

Hi Rick,

It looks like the 5200F is a European model only which possibly could be the problem with installed a US version of the software (but that is just a guess).  If you still are having problems try this link from the Canon UK downloads:


# Shavaj said on 15 January, 2012 03:37 AM

Many thanks. Path variable was the issue

# richard p said on 16 January, 2012 06:17 AM

Windows 7 64 bit and a Canon 5200F. I had this problem, and went nack to the Canon 4.9 Toolbox, and with your path set, - it worked. Thank you.

# Chris said on 17 January, 2012 01:53 PM

Win7 64-bit and a CanoScan LiDE 25. You saved my life, thank you!

# Darrel said on 20 January, 2012 08:36 PM

Thank you so much!

# Catherine said on 22 January, 2012 02:00 PM

Windows 7, 32 bit, Canoscan Lide 90. Used to work fine until now, when I had to replace my HD on my computer (it also doesn't work w/my new netbook, Windows 7 starter 32 bit). I think it might have to do with the new 5.0 version - I had been using 4.9 or earlier, I think, with no problems.

I looked for the C:\Windows\twain_32 folder and found two CNQ folders in there (2411 and 2412). I tried inputting the path for one, then the other, but neither worked. Should I put in both?

# David P. said on 23 January, 2012 07:55 PM

It worked!! Better than some of the other solutions that are out there. Thanks so much.

# kaneXtreme said on 27 January, 2012 06:35 AM

Wow. I was reinstalling my driver everytime i come across this problem. Now its fixed forever! Hopefuly.

Thank you so much for this wonderful article! ;)

# Delbert said on 03 February, 2012 06:55 AM

That workded. You're a saviour.

# LIN said on 04 February, 2012 12:45 AM

Hi I need your help!!!

I'm using canoScan 8400F.

I followed your instruction but the window still pop out:

Unable to open TWAIN source

Please check connection

Then restart toolbox

Any advise?

# Olaf said on 04 February, 2012 06:49 AM

Thanks Jeff - this method works fine, but only after I added a backslash \ at the end of the path.

# Phillip King said on 06 February, 2012 04:39 AM

Thanks for the info!  Much appreciated and saved me the hassle of the usual uninstall / reinstall / repeat cycle!

# Helenmary Cody said on 06 February, 2012 12:59 PM

Thanks for posting this! I've wasted a LOT of time trying to figure out why my scanner no longer wants to scan and this fixed it in less than 5 minutes. I wish I had found it sooner.

# jhen said on 07 February, 2012 10:07 AM

Thanks for posting this. It was really a lot of help. At last I am able to successfully scan my document.

# Toprope said on 09 February, 2012 04:47 AM

Thank you so much, it works!!!

# Eythor said on 21 February, 2012 04:15 PM

fantastic, I have tried everything but nothing worked until I tried your way.. thank you!

# Dennis said on 24 February, 2012 12:52 AM

Thank you. I've been looking for a solution for quite some time.

# Skevos Mavros said on 24 February, 2012 01:50 AM

Worked like a charm.  THANK YOU.  I still don't know how my path variable got erased, but who cares, it's fixed now.

For those that have scrolled this far but for whom it didn't work, first install your driver, then go looking for its folder in C:\Windows\twain_32 (yes, even Windows 7 64 bit puts it in a folder called twain_32).  When you find it's folder name, then add that as described above - each scanner model has a different folder name.

# jessie said on 25 February, 2012 01:41 AM

hi im using canon ir2318, also i am trying to set up my scanner i also had the same problem. is this procedure is applicable for me. thanks

# Frred said on 25 February, 2012 04:49 PM

This solved the problem. The problem had NOT occured on a different computer running an identical OS (XP SP3), but with older hardware. Was dumbfounded as to why the error appeared on the newer computer. Thank you!

# Nico008 said on 26 February, 2012 07:30 AM

Thank you very much!!! This works fine for my CanoScan 4400F!

# Wes said on 28 February, 2012 03:30 PM

Kudos!  Two and a half years later, and the info is STILL valuable. Let's hope this entry stays around as long as it's needed. BTW, this method worked for me on Windows XP and LIDE 80 combo.

# pg said on 29 February, 2012 07:05 PM

Thanks! worked for me - Win 7/64, Canon 8600F

# Suparoo said on 01 March, 2012 04:56 AM

I have tried every one of the above fixes for a Win7 Home 64bit installation, even upgraded PhotoStudio 5.5 to v6.0 and still get the same error "Unable to select TWAIN source".

We have uninstalled everything and started from scratch, still in the wilderness with this scanner.

# Eric said on 09 March, 2012 02:29 PM

Thanks so much for making my day easier. Worked perfectly on CanoScan LIDE 60 on Windows 7 64 bit os!

# naj said on 09 March, 2012 03:47 PM

Thank you so much!


# Inga said on 10 March, 2012 12:37 PM

Jeff - your trick is still working - thank you so much for such a clear post on this.

Best wishes


# TD said on 12 March, 2012 02:11 PM

Awesome!  Worked for me too!!!

# vage said on 14 March, 2012 03:08 PM

I confirm this one too!!

# PoorBruce said on 15 March, 2012 03:26 PM

Worked for me!  Thank you very much!

# icaneo44 said on 16 March, 2012 01:41 PM

Works for canon lide25

# crocdoc said on 20 March, 2012 02:25 AM

Thanks SO much. What can I say, it worked!

# Dave said on 20 March, 2012 04:34 AM

Just want to say thanks a lot for this! Google definitely put the most helpful answer at top of list!

To confirm, this works in the UK for a CanoScan LiDE 70 on a Dell OptiPlex 990 running Windows 7 Professional 64 bit. I used CanoScan Toolbox and ScanGear CS driver 12.11 from Canon's website.

# Walid Kalam said on 20 March, 2012 12:14 PM

thank you vry much its was vry helpfull to me and if it wasnt u i would hav failed in my project.............

# Don Thomas said on 20 March, 2012 11:02 PM

Reinstalling the software didn't fix the problem, but your solution did. You saved me a major headache, Thank you so much!

# Joe said on 24 March, 2012 09:38 PM

You're awesome.  And then some!!!

# Rob said on 26 March, 2012 10:35 AM

I think this is still the definitive source on the internet for solving this problem. Thanks!

# Jorn said on 29 March, 2012 02:18 PM

I tried your fix on a Canoscan LIDE 30 (with win7), but it didn't work. After much fiddling I finaly reached the goal. First: The driver ScanGear CS v7.0.3.1a did work all the time (I could hear and see it when information was exchanged with the scanner and the scanner started up). The problem was my newest toolbox program. Some time ago I downloaded CanoscanToolbox4.932en_win7-Vista-xp.exe from Canon site. But this program was not able to find the driver, no matter what I did. Instead I installed CanoscanToolbox_v4.136enVista.exe and it worked immediately :-)

Nice to see that your advise have helped so many people! :-)

# Bob B said on 04 April, 2012 09:21 AM

Seems to have worked for me too Jeff. Running a 4400F under Win7 32bit. Problem appeared a month or so ago and likely to have been Win7 SP1 or installation of Adobe Photoshop/Premiere Elements 10 that caused it as both changes happened about the same time. Have been puzzling since then (though still able to acquire scans through Photoshop so thought problem was Toolbox rather than driver). Then found your posting - what a hero!

# Petr K. said on 06 April, 2012 08:53 PM

Thanks a lot for this solution, I have the same problem with Canon LiDe 60 on Win7/64b. I have changed many types of drivers, try compatibility modes etc. Now I am knocking my head against the wall ;) Everything is ok now. It works. Thank You again.

# Zubair said on 10 April, 2012 11:39 AM

Thanking you so much for the advice...I added the environment variable and it fixed it.

# Laura said on 11 April, 2012 05:57 PM

Wow, you know how much time I wasted on this until i found your tip!! Very long phonecalls with Canon helpdesk, emails with them, no one could help me.

Thanks you very much!

# John said on 14 April, 2012 04:46 AM

You would think that Canon would know this!

Thanks very much!

# Roger said on 15 April, 2012 04:53 PM

found this solution just five minutes before buying a new scanner .... I suppose that Canon don't want to provide such an easy solution rather than providing new scanner hardware to increase their profit ....

Thank YOU!

# Sean Achim said on 16 April, 2012 07:52 AM

Brilliant - Thank you SOOOOO much.  It's amazing that in April 2012 this is still a problem that is so simply solved and is not listed on the Canon website as a solution.  You are my new hero and  you don't even need to grab the nearest tablecloth to wear it all week as a cloak with your underwear outside of your trousers:)

# Alberto said on 18 April, 2012 07:47 AM

It Works !!!

thanks a lot !!

# Jean-Yves said on 18 April, 2012 11:18 AM

It Works, thanks you so much!

# Dan A. said on 18 April, 2012 04:07 PM

Absolutely worked!  You saved me a lot of grief.  Thanks!

# Billr said on 22 April, 2012 05:53 PM

I've been using W7 64-bit operating system on my laptop for about 18 months. My scanner worked perfectly until last week - Suddenly I started getting "Unable to open TWAIN source" error. I couldn't find or do anything to get it to work until I found your very well explained fix. Many thanks

# Mark D said on 27 April, 2012 07:38 PM

Another success. I was going to toss this hand-me-down LiDE30 in the trash. No need now to buy a new one. Thanks.

# Houda said on 27 April, 2012 09:39 PM

I can't seem to find any folder within the TWAIN folder, I can only find the "wiatwain.ds" file, nothing else. Any one know why?

# chanmmn said on 04 May, 2012 09:08 AM

Great post !! Thanks

# Chris said on 08 May, 2012 03:25 AM

Running LiDE 70, Canon Toolbox on Win7 x64. Path fix did NOT work as others have reported for this version.

But here's what DID work: run the Canon Toolbox app as Administrator. It's working for me without doing anything with path.

# Ken said on 13 May, 2012 05:22 PM

Worked great for my CanoScan 4400F on Windows 7 Ultimate.  Thanks!

# Jimbo said on 14 May, 2012 01:46 PM


Thanks for posting this article! I could tell that both my drivers and the application to drive my older Canon f9950 were installed and functional... but it did not occur to me that the PATH (or lack thereof) would be the culprit in the failure to "communicate". Win 7 Home Premium.

# Antony Zaglas said on 30 May, 2012 09:34 PM

Many thanks for the solution it is rare that such precise advise is found on the web

# Micha109GE said on 03 June, 2012 05:59 AM

Hello Jeff,

thank you very much for posting this solution, it worked out fine for me.

I own a Canon LIDE500F scanner and run Win 7 64.

# mehdi said on 04 June, 2012 05:50 AM

man, thank you so much, after long time that i wanted to buy a new scanner i could use it again :) god bless you

# somites said on 11 June, 2012 02:18 PM

ur an absolute genius dude !!!! u solved my problem in a jiffy !!!!

# Philip said on 13 June, 2012 03:09 AM

Fantastic straight forward information! My CanoScan LiDE 60 stopped working for some reason. Now, it is working again!

I wonder why the CanoScan toolbox isn't able to handle this issue or at least return a meaningful error message!

Because, obviously this trivial problem is causing trouble and time loss to thousands of users.

# Arlo said on 21 June, 2012 05:55 AM

You rock, fixed the problem for my LIDE 30 scanner

# Ted said on 25 June, 2012 05:49 PM

After a reboot worked like a charm!.

Many thanks.

# David Davenport said on 27 June, 2012 12:54 PM

You the man!  Thanks for the quick/easy fix!

# Lupe said on 29 June, 2012 02:16 PM

Thanks!!!!! Fixed my LiDE 25 on Win 7 x64

# Nenad said on 06 July, 2012 12:22 PM

Wow! This fixed my issue too on WinXP SP3 for Lide 600F. Thanx for the tip!

# Cathy said on 12 July, 2012 04:53 PM

Brilliant!  Thanks for the screen shots too!  We technically challenged need all the help we can get.

# Mark said on 14 July, 2012 11:38 AM

Jeff, you are a star *.  Fixed my canon  Scanner LIDE 600f on Windows 7.  Thank you very much.

# Linczy said on 16 July, 2012 07:30 AM

Lide 25 users with windows 7.

Exactly same problem after setting this additional directory to my path environment variable. :(

# Tony H said on 18 July, 2012 01:24 PM

You, sir, are a life saver. Worked perfectly on Windows7 (64-bit) with a Canoscan 8600F.

# Andrea said on 20 July, 2012 01:41 AM

I spent half an hour installing/reinstalling drivers, searching new versions etc, because it didn't work.

Then I discovered your page, and after one minute my Canoscan lide 25 is back to life !

Thank you so much !!

# Otto S. said on 25 July, 2012 05:24 PM

Thankyou for the solution. Thanks for the quick/easy fix!

# Shaz h said on 29 July, 2012 05:00 PM

You are an absolute genius! Spent months researching this and saw something on another forum but not as clearly explained as this!


# Bruno said on 01 August, 2012 02:15 PM

Thank you very much, It worked for me: to install the Canoscan Lide 25 on Windows 7 x64. I had been trying the solution from the official Canon and windows websites, it was not working. I had been trying various solution found on the internet: in vain. You solved the problem. Thank you.

# Esteban said on 08 August, 2012 10:04 PM

You are great, works like  a champ.THANK YOU

# Faizal said on 08 August, 2012 10:50 PM

Scanner worked like a charm for many years and then suddenly stopped working. I suspect some recent Windows 7 upgrade or other software clobbered the PATH. The PATH solution worked for my LiDE 60! I am computer programmer with lots of experience and it would have taken me a lot of time and so you saved me a lot of headache!

# Krish said on 13 August, 2012 02:13 AM

Thanks, I was holding on fixing this for days before I googled this.. Today I didn't have my wife's laptop to use my scanner and didn't have a choice but to find a solution. This tip worked for me (Win 7) and many thanks..

# themanmachine said on 15 August, 2012 06:36 AM

thanks, thanks, thanks.

Canoscan Lide 600F - Vista Ultimate x64

# Michael Cook said on 16 August, 2012 01:54 PM

Thank you very much...

# Lisa said on 17 August, 2012 04:37 PM

Yep, you helped me too!  Woot!   Thank you so much!

# Dave Qnir said on 19 August, 2012 11:39 AM


Just bought a Win64 laptop, and I must have installed, uninstalled, and re-installed the software and drivers a dozen times. Rebooting like a madman didn't help, either. Just a simple addition to the path and all is well.

Thank-you thank-you thank-you.

# Hilary said on 21 August, 2012 03:06 AM


I was fighting with this bothersome problem for years. I installed and unistalled drivers and Toolbox I don't know how much times and sometimes it didn't work..

And now with this simple trick it's all ok!

Really thanks so much

# David Peck said on 22 August, 2012 08:54 AM

You're a diamond geezer! Thanks so much.

# Sandra Madden said on 26 August, 2012 01:29 PM

awesome. Thanks a bunch. this fixed it for my Lide 70 :-)

# Medman said on 26 August, 2012 10:09 PM

I must have installed & uninstalled Canon's drivers a dozen times on my new computer, but the TWAIN scanner was not recognized on my Canoscan 8600F.

Finally bumped into your page on a Google search & poof it works great!

Thanks for posting a simple, but very effective fix!

# Phil said on 27 August, 2012 07:35 PM

Another satisfied customer.  Fixed my problem in 2 minutes!

# Pavel said on 11 September, 2012 04:12 PM

Thanks, it solved TWAIN problem at 4400F right away!

# Seba said on 12 September, 2012 03:39 PM

Thanks. i've lost two hours installing and uninstalling damn drivers and software :)

# LaVenus said on 15 September, 2012 02:02 AM

Worked like a charm!! Thank you for providing the step by step!

# Eric said on 21 September, 2012 10:49 AM

Thanks!  After a Windows update and some other installs, my scanner suddenly started presenting this error dialog.  Adding the twain path fixed it.

# Paul Marangoni said on 23 September, 2012 05:34 PM

No luck here. Modified the path variable, but still getting the error. Windows 7, 64 bit, Canon CanoScan 8400F.

CanoScan Toolbox

# Peter Clark said on 25 September, 2012 01:33 PM

I modified Path and it seemed not to work, but I had to close and re-launch Photoshop, the destination application.

Then all was well! (LiDE 25, XP)

Thanks for the solution.

# Sepehr said on 03 October, 2012 02:24 PM

Thank you so much :)

# Erik Siegel said on 07 October, 2012 08:33 AM

Bingo! Thanks a lot.

# Kamran said on 15 October, 2012 04:23 AM

Many Many Thanks.

It works great, I was disappointed but .... ;)

# Joe said on 16 October, 2012 05:42 PM

Don't know if this has already been posted, but for Windows 7 64-bit users, CanoScan Toolbox 5.0 does not work, but 4.9 does.

# Ed said on 17 October, 2012 05:14 PM

Perfect! Worked like a charm, thank you!

# Rick said on 18 October, 2012 10:24 PM

This was a huge help. Thanks!

# tadas said on 19 October, 2012 08:08 AM

many thanks!

Did it very fast.

# Rod said on 19 October, 2012 05:47 PM

Excellent, concise solution. Thanks!

# Martin said on 20 October, 2012 11:07 AM


thanks for a perfect hint.

My configuration: Windows 7 64x, LiDE 500F

At first adding the path did not help.

Then, I tried varous things (like not starting WIA service, checking the limit of PATH variable length, starting the Toolkit as admin/ in compatibility mode, ...).

Eventually, I noticed that in the PATH variable, all items are separated with semiolon ONLY.

I removed the SPACE after the semocolon before my path to the twain drivers.

AND IT WORKS - [amazing that] this matters in the 21st century - my goodness.

All those who posted that the hint did not help, chech please for the extra SPACE .-)

# Mike said on 22 October, 2012 10:38 AM

Thanks!  Got my scanner operating quickly.  Such a simple fix, but so deep in the details.  Amazing.

# Harry said on 22 October, 2012 08:21 PM

Thank you so much! It really helps me!!

# Clayton said on 22 October, 2012 10:07 PM

Worked great.  Mine was a Canon 500F, and the file was ;C:\Windows\twain_32\CNQL500

Note no spaces

Thanks alot, this saved hours of heart ache.  Canon owes you a beer!

# Thomas Darlington said on 24 October, 2012 10:20 AM

Thanks a bunch!  This worked for me as well with a Canon 4400f on Windows 7 x64.

# Sinuhe69 said on 25 October, 2012 03:32 AM

You save my day Jeff! Why Canon did not have this kind of information and let its customer setting in the dark?! In all Canon support forums and portals, no word even mentioned about this particular disdainful problem.

# Sascha said on 25 October, 2012 05:59 PM

Wow - this is the first time I have had success with online help!! Many thanks!!!!!!!!!!!

# Christian said on 26 October, 2012 02:00 AM

That did the trick. But what I don't understand is, why it suddenly got this point. Thanks for the help.

# Trevor Heaton said on 28 October, 2012 01:49 PM

Got it working now. Can't understand why it used to work but then decided not to.  Good job there's young people like you who can find out how to sort it.

# WPW said on 08 November, 2012 04:25 AM

WOW! It works. Thanks a lot.

# alexm1003 said on 08 November, 2012 05:11 PM

Many thanks, I spent 2 hours searching the internet in vain for a solution until I found this page. Now I got it working. Shame on Canon for ignoring this problem.

# Jack said on 12 November, 2012 05:12 AM

Thank you so much. You are really superman. Mine was a CanoScan LIDE25, and now it can work in my  win7(64bits).

# Richard said on 18 November, 2012 04:52 PM

Thank you sir.  This was very helpful.

# Alan said on 18 November, 2012 11:36 PM

Thank you !!!!  Life saver !!

# David said on 24 November, 2012 09:26 AM

It's people like you that actually help the world go round.

Been trying to get a LiDe35 to work under W7 64Bit for 6 months and this was the missing bit, Thank you sooo much

# Gerald said on 29 November, 2012 05:50 AM

Thanks so much.

However, it is unacceptable that one needs to do manually what should be done automatically.

# Finn Cannon said on 30 November, 2012 04:03 PM

It's a CanoScan LiDE200, and I'm running Windows XP. I followed the directions *exactly*.

Good directions, by the way.

Pity they didn't work, though. Absolutely no change to the twain error message.

# Hollis said on 02 December, 2012 08:35 PM

Thanks for this.  Worked great with CanoScan 4200F

# Jaime said on 11 December, 2012 09:13 PM

Thanks!  I thought I'd have to buy a new scanner to replace my aging Canoscan LiDE 500F, but this worked a treat. I'm amazed that people such as yourself go to so much effort to create step by step instructions like this for the rest of us.  Thank you for your time, effort and knowledge.

# Cesar said on 12 December, 2012 09:34 PM

Mil gracias por la solucion inimaginable desde mi experiencia pero dio con la solucion!! gracias buena solucion.. saludos

canon scan lide25 en win7 64b

# ima said on 13 December, 2012 10:20 PM

Thank you so much!!! It really worked on my PC. Now I can use my scanner canoscan 4400f.

# Andrew said on 14 December, 2012 04:19 PM

Thanks.  Saved me buying a new scanner.

# danny maserati said on 14 December, 2012 08:32 PM

Thanks it works , you was save me

# Vaidas said on 15 December, 2012 06:12 AM

Thank you very much for solving this annoying thing! More than one year I was using older computer for scanning only...

# Daniel said on 16 December, 2012 02:47 PM

This was extremely helpful, had no problems until today and have owned the scanner 6 months. This helped me solve the issue quickly.

# anonymous said on 16 December, 2012 05:53 PM

Thank you for posting this fix.  I finally got my Canon lide35 scanner to work in W7 64-bit after using the lide60 driver and your path instructions.  Glad that I can still use this old scanner which was a really good model.

# anonymous said on 17 December, 2012 06:41 PM

Thank you so much for your article. Made my day :-)

# Fritz said on 18 December, 2012 04:57 AM

You Jeff are real star :) :)

Works unter Windows 7 Home Premium

NOTE to everyone: Do not try to run the LIDE 500F via an USB Hub on Windows 7, that does not seem to work properly and Windows has major issues to reach the CanoScan.

Uninstall driver at System Config, then Add Path as mentioned above, plugin Scaner DIRECTLY at Computer/Laptop - restart, reinsriver from Canon Website - restart once again, enjoy!

# John said on 18 December, 2012 06:48 AM

Tried the path thing to no avail. Running Win 7 Premium on Dell Latitude Laptop. Scanner is a LiDe 600F. Tried uninstalling drivers etc etc - nothing. Reading back through all the comments I found one which said much the same but got it to work by running Canoscan as Administrator and voila! it worked ...about 3 hours wasted. Clearly it has come about from a Windows update!

# Dennis said on 18 December, 2012 08:26 AM

I had just about given up expecting to use my Canoscan 4200F on Win 7 64-bit Home Premium. Last year I read heaps of advice, mainly about deleting old drivers and installing the latest version from Canon, but all to no avail. Today I had another bash at it, was just about to throw in the towel again, and then found your page. yes, adding the variable to PATH was all that was needed. Why couldn't Canon get that right?

Thank you VERY much indeed.

# Darrell said on 27 December, 2012 11:40 AM

Worked like a charm, thanks!

# Claude pattaya said on 30 December, 2012 10:38 PM

Thanks, Happy new year

# Tony said on 03 January, 2013 07:05 PM

THANKYOU THANKYOU THANKYOU!  I was on the phone with Canon support for over an HOUR, and they did not know this. Just changing the path worked!!

# Rekha said on 05 January, 2013 12:28 PM

Setting PATH didn't help me either. Running Toolbox as Administrator helped me.

Thanks for this article.

# Victor said on 10 January, 2013 10:40 AM

Muchas gracias desde Chile

# Tony B. said on 14 January, 2013 02:31 PM

Perfect solution to the problem.  It worked like a charm.

# Lukas said on 15 January, 2013 04:19 PM

Many thanks, very simple and WORKING solution. It helped me very much.....

# Hendro K. said on 16 January, 2013 12:38 AM


Thanks a lot for your solution. It fix my frustation in using my CanoScan 4200F in Windows 7 x64. It perfectly works as expected.....

# Multicore said on 22 January, 2013 09:32 PM

Fixed my 8400F under Windows 7 x64 and Photoshop CS2. You're the man.

# Paul said on 24 January, 2013 07:45 AM

I thought I'ld never be able to use my 4400F to scan slides again after upgrading from Windows XP to 7. Until this morning when I found your solution. Thanks a lot !

# Dave said on 26 January, 2013 09:02 AM

Tahnks Jeff!!!

have a 600f scanner work great my folder was name 4802 instead of 4803 changed the 3 for 2 and away we went.  Thanks

# Josip said on 28 January, 2013 08:07 PM

Thanks a lot, to others please, check all zour steps again ... I forgot to write semicolon and was not working ... then read again and check all step by step now is working , thanks again

# Urs said on 29 January, 2013 02:59 PM

Thanks Jeff!

This is the solution for my old Lide 60 scanner.

# Jacob said on 31 January, 2013 02:16 PM

Thank you very much for this information!

# Joe said on 04 February, 2013 04:51 PM

This worked for me, old CanoScan LIDE60 scanner on Windows 7 Enterprise 64-bit. Thanks!

# Andrew said on 06 February, 2013 01:45 PM

Thank you very much!  I would never have figured it out.  CanoScan 8400F

# tony goodwin said on 18 February, 2013 03:30 PM

ABSOLUTELY WORKS! I was going to buy another scanner!  Thank you!

# Sean said on 19 February, 2013 05:36 PM

Quick, easy, simple and makes my scanner work again!

# Xuan said on 22 February, 2013 05:29 PM

You got me setup right - you da man!

# Agi said on 28 February, 2013 03:28 AM

Thank you so so so very much!!!!! I did not understand what i was doing, but i followed your instructions and it is working now!!! :)

# Jim said on 01 March, 2013 02:31 PM

That did it!  Wish I would have found this a couple of years ago!

# Joseph said on 19 March, 2013 08:58 AM

Many thanks - very helpful!

# Richard Rixham said on 22 March, 2013 05:58 AM

Thanks for this information. I have been trying to get my Lide70 working and this resolved my issue. Cheers.

# Khoi said on 22 March, 2013 01:57 PM

I have a 500F and if you follow his instructions, it should work!

Windows 7 64 bit

Path: C:\Windows\twain_32\CNQL500

Double check yours...

# Adam said on 23 March, 2013 04:59 AM

THANK YOU SOOOOOOO MUCH... Huge help!!!! Thanks for your time and being such a great help...Cheers!!

# Matt said on 28 March, 2013 01:08 AM

thanks so much for posting this information

# Mark said on 29 March, 2013 07:55 PM

This worked and you are a genius...thanks so much!  

# Tom said on 01 April, 2013 04:39 PM

Worked for me. Many thanks!

CanoScan LiDE 500F

Windows 7 64

Path: C:\Windows\twain_32\CNQL500

# IanJ said on 05 April, 2013 03:11 PM

Thanks for this info!  This has been biting me for a while - some windows update or something stuffed up my Canon LIDE600F Scanner on Win7/x64, and no amount of reinstalling seemed to fix it.  This works a treat! :)

# larry said on 05 April, 2013 08:59 PM

thanks a million! Canon wasn't even able to fix this for me.

# Richard said on 18 April, 2013 10:52 AM

Thanks so much. Worked for me.

# MIchael Rice said on 21 April, 2013 02:51 PM

The really great part about this is that I was able to apply these steps in Windows 8.

After running the driver and software installation in Windows 7 compatibility mode, I applied your steps and now my beloved 8400F can move on to the next generation of Windows OS with me.

Great tips, well written. I am going to steal the phrase 'OK your way out'. Thanks! :)

# noghere said on 23 April, 2013 03:17 AM

Great job! FANTASTIC! Many thanks from Italy.

(CanoScan LiDE 600F Win7 64bit)

# Rehan said on 24 April, 2013 12:12 PM

Thanks so much - this solved the problem which I have had for almost a year, since I went over to Windows 7 64bit!!!!

# Valentin Despa said on 26 April, 2013 01:23 PM

Thanks for sharing this! Many thanks for fixing my LiDE 25.

# Saleh said on 27 April, 2013 05:02 AM

Jeff your solution have been working for years!. I installed my CanoScan 8600f on a new laptop  which came with Win 8 X64  and confronted with the same problem. your solution worked just fine. Many thanks.

# Vicky said on 30 April, 2013 03:48 PM

Thank you so much for this info. My Canon 4200f now is working properly

# FAbrizio said on 04 May, 2013 11:41 AM

Yeah ..... it worked.

My 4400F was unusefull without canoscan toolbox.

Tks a lot


# kent said on 08 May, 2013 04:48 AM

Thanks a million!! it works!

# LARRY G said on 08 May, 2013 01:18 PM

i have the same twain source problem but on canon lide 60.....does the posted insrtuctions apply to lide 60 ?

# Arlene DeBoer said on 13 May, 2013 10:14 AM

I have the same problem with my Canon D530.  It worked fine with my lap top, I just a new computer with windows 8 (I hate windows 8) on it, and I have to keep restarting the computer to get the scanner to work.  I tried what the canon support people told me to do, but that did not work.  I changed the path like you said above, but it it still is not working right.  If I keep right on scanning it is ok, but if I stop for a while it will no longer work without restarting the computer.  I am very frustrated.

# Sergey said on 16 May, 2013 03:04 PM

Thanks a lot! Working!!!

# Zupahome said on 19 May, 2013 04:49 PM

Got it fixed thanks to you!

# M1Lithium said on 27 May, 2013 11:35 PM

Awesome - Worked Perfect. Thanks.

# Slicray said on 31 May, 2013 12:14 AM

Thanks, very useful info.

# Rich H said on 03 June, 2013 09:00 AM

Our Canon scanner has periodically had issues requiring us to reinstall the software. But we just moved the scanner to a new computer, installed the software and then started getting the "Unable to Open Twain Source" error message.

Your fix worked like a charm. Thank you for taking the time to create such detailed instructions!

# A Falk said on 05 June, 2013 11:45 AM

Hey. Thankx a LOT! Sweet spot!

# AP said on 06 June, 2013 09:48 AM

Thanks, this fixed my scanner problem too.

# Amanda C said on 08 June, 2013 11:41 PM

I tried Jeff's fix in the past and it didn't work, but after coming back and reading the comments, I tried just installing the newer version of the CanoScan Toolbox ver. 4.9 that's been updated for Windows 7. IT WORKED! Here's the website: The download box is near the bottom. Again, don't use Toolbox 5.0, it didn't work for me (Win 7 64-bit). Thanks to everyone with their input! My beloved Canon LiDE 25 are reunited once more :)

# Arlene DeBoer said on 09 June, 2013 08:16 AM

I am trying for help again, the scanner works fine the first time in the day that I am using it.  When I try to use it again a couple of hours later , it keeps saying the server is busy and to switch applications, when I do that it still says that the scanner is busy.  (Canon D530)  I am wondering if the store will take it back, because I am totally aggravated with it.  I have tried posting several times, I see only the first post, not the consecutive ones, so I am not sure this is getting to you

# Tony Simmons said on 13 June, 2013 08:39 AM

This is the post that, after 3 1/2 years, just keeps on giving :-) Thanks Jeff

# Joey said on 15 June, 2013 04:41 PM

It didn't work for me. I am about to give up. When I first bought my canoscan9000F it worked beautifully with my Windows 7-64 OS. Now, immediately after scanning a photo, I get that stupid message, and then it stops working.

# Nanda said on 20 June, 2013 06:25 PM

Wow, worked like a charm !!!

# Sharada Prasad said on 21 June, 2013 12:19 AM

I also faced the same problem:


CanoScan Toolbox


Unable to open TWAIN source

Please check connection

Then re-start Toolbox


I could not find any subfolder in C:\Windows\twain_32

I tried installing the latest software from Canon website. Even that did not work. I then followed Amanda's instructions and it worked perfect.

Thanks to you all!


# Amanda C said on 08 June, 2013 11:41 PM

I tried Jeff's fix in the past and it didn't work, but after coming back and reading the comments, I tried just installing the newer version of the CanoScan Toolbox ver. 4.9 that's been updated for Windows 7. IT WORKED! Here's the website: The download box is near the bottom. Again, don't use Toolbox 5.0, it didn't work for me (Win 7 64-bit). Thanks to everyone with their input! My beloved Canon LiDE 25 are reunited once more :)


# Ted Bodfish said on 25 June, 2013 12:06 AM

Worked well. Thank you.

# Phil said on 25 June, 2013 06:37 AM

Another happy customer!

# Lucky Tech said on 25 June, 2013 11:09 AM

You saved my bacon......and that's all that needs be said.

Heaven or Monaco, it's your choice.....

# Don said on 26 June, 2013 01:47 PM

Thanks man!  Got my Cannon Lide 70 working again!

# Matt said on 02 July, 2013 04:07 PM

Holy S*&T!! I've used my scanner for years with no problem. Then, all of the sudden, nothing. I literally had it sitting at my garbage when I found this and like magic it works again! You, sir, are amazing.

# Birger Mess said on 09 July, 2013 04:05 AM

Canoscan 8400f now running on Windows 8 ! Thank You Elliphant for your advice in this thread.

I had tried some other combinations of known 64-bit drivers for other models and different toolboxes, but ended removing it all and deleting the twain drivers in despair. Then I came back for one last shot and found Elliphant's link to the proper 64-bit Windows 7 driver - filename 8400fvst6410231a_64en - and installed Toolbox 4.9 - filename CSTb4931WNEN.

Worked like a charm!

BTW, I too had a fling with Toolbox 5.0 at another time, but couldn't get it to work and reverted to 4.9 with success. I'm through wasting time on /that/ experiment

# Zsolt Varga said on 12 July, 2013 04:19 AM

Thank You! The only clean and precise documented solution for this problem.

Canon: update your drivers !!!

# Alexander said on 16 July, 2013 02:05 AM

Thanks a lot! It helped.

# Taylor said on 16 July, 2013 09:36 PM

It works! Thank you!

# Chris said on 17 July, 2013 04:50 PM

Great job, it worked for me. Thank you

# Dave said on 19 July, 2013 08:53 AM

Canon LiDE 500F working fine in Win8_64 ONLY AFTER APPLYING this PATH solution (and Win7_64 drivers)!  Thank you Jeff!

# techN said on 24 July, 2013 11:33 AM

Thanks a lot! Working perfect

# Slava said on 28 July, 2013 02:12 AM

Thank you a lot! Helpful!

# Rachel Williams said on 30 July, 2013 07:46 AM

Brilliant! Works a treat! Thank you!

# Michael said on 31 July, 2013 01:16 AM

Worked for me, this is what I wrote: %SystemRoot%\system32;%SystemRoot%;C:\Windows\twain_32\CNQL25

# Dema said on 01 August, 2013 07:50 AM

You are my hero! Thanks a LOT!

# Rosalie said on 06 August, 2013 07:08 AM

Awesome! This article is fantastic - fixed it up :)

# jEFF said on 09 August, 2013 12:41 AM

Thanks a million, after a couple of frustrating hours of misinformation, i found your article. Everything now working again

# Uyi said on 09 August, 2013 12:19 PM

Wow! Thanks a lot!! My scanner now works:)

# tibor said on 16 August, 2013 04:28 AM

thank you

# Lucyda said on 19 August, 2013 02:46 AM

Thanks for the advice. I had to create a new path variable though, but it worked at the end. Much appreciated!

# cr4711 said on 21 August, 2013 06:03 PM

Hey Jeff, thanks a lot for the advice! Finally solve my Connection Problem!!

# ChrisL said on 24 August, 2013 11:34 AM

Hi Jeff, thanks so much for posting this solution! I'm not sure why this problem started all of a sudden. But I suspect it is related to a recent system 'cleanup' that I did

# Bugsy said on 24 August, 2013 12:57 PM

Thanks heaps! This worked a charm.

# Adamb said on 27 August, 2013 02:43 PM

Worked like a champ. All I had to do after following the instructions was to restart the toolbox for my lide 600f

# reader said on 27 August, 2013 04:14 PM

Good post, clear and direct!

# John said on 29 August, 2013 05:07 PM


I only needed to read the first two lines. Why cant Canon have this on their knowledge base. WHY??? Because Canon, you can't!

# Luke said on 30 August, 2013 06:00 AM

Thanks a lot - this worked like a charm! Keep it up and all the best.

# Patrick said on 03 September, 2013 10:26 AM

I was just about to throw away my scanner when I came across this website. Thank you Mr. Widmer you just saved me from having to buy a new scanner.

# Ruben said on 03 September, 2013 03:55 PM

Thank you! Problem solved. I can still use this scanner.

# Mikael said on 05 September, 2013 02:40 AM

Thank you very much for this information! I would never have solved this without your help, and I am so happy to be able to use my scanner again. A very big thank you goes out to you from Sweden! //Mikael

# david said on 05 September, 2013 02:35 PM

Great, worked just fine. Many thanks!

# Mano said on 07 September, 2013 05:10 AM

Now my old Canon lide 25 works again.

You were so precise in your solution, Thank you!

# Saskia said on 07 September, 2013 03:52 PM

Great.. got it finally to work! Many, many thanks!

# Robert said on 09 September, 2013 04:39 AM

Another 4200F fixed, thanks!

# Guenther said on 09 September, 2013 07:48 AM

This info us so usefull. My LIDE 35 (for Win7-64 use driver for LIDE60) was working for 2 years and then stopped. Now it is working again!! Thank you sooooo much.

# Cynthia said on 09 September, 2013 04:03 PM

Fantastic! It worked like a charm. many thanks

# WOWZIE said on 10 September, 2013 12:25 AM

Canon MF3240 working great in Win8_64 AFTER APPLYING this PATH solution (and Win7_64 drivers)!  Thank you Jeff!

# Rana Anand said on 11 September, 2013 01:29 AM

Thank you kind sir! Worked like a charm!

# Nenad Bulatovic said on 12 September, 2013 09:10 AM

Thank you - this is right solution for this problem!

# Ryan J said on 17 September, 2013 07:52 PM

It's 2013 and I know I should get a new scanner... but I think you just gave me a couple more miles with this one.  Thank You!

# Nick said on 20 September, 2013 08:40 AM

Works for Canoscan  lide 35. THanks!!!!

# tommein said on 22 September, 2013 12:29 PM

Installed Visual Studio 2013 RC and my Canon Lide 25 stopped working.

This solution worked for me, thank you

# Susannah said on 22 September, 2013 02:56 PM

Help please! Even this perfect trick didn´t work.. I´m desperate! I have a CanoScan 9900F and it suddenly doesn´t want to work- like in many other cases.. But unfortunately Jeff´s advice didn´t help. I truly have no idea what to do now.. Does anybody, please, know another possible way how to solve it? Thank you!

# Stan Greenberg said on 25 September, 2013 09:46 AM

Not just a Win7 or 64-bit problem - spent hours installing/uninstalling searching for bugs on a WinXP

machine - til I found your comment, and bingo 5

minutes later the scanner was up and running.

A thousand-times thanks.  Wish Canon would

acknowledge this path bug.


# Guenter Rieker said on 30 September, 2013 09:31 AM

Thanks, solved my problem

# greywarrior said on 30 September, 2013 05:58 PM

Excellent! Worked for me, thanks!

# PreshawPete said on 02 October, 2013 12:47 PM

Thank you Amanda C - version 4.9 works for me when 5.0 did not

# Kamal said on 05 October, 2013 11:37 PM

Thank you! Your post helped me fixing this same issue with my Canon 4200F on Windows 7

# Alex said on 06 October, 2013 03:38 PM

Problem solved. (CanoScan LiDe 25, Windows 7)

Thank you, Jeff!

# Ed VandenDool said on 09 October, 2013 02:31 PM

Thank you!!! This worked perfectly after I had spent a LOT OF TIME uninstalling and reinstalling repeatedly to try to solve my problem. Your instructions are excellent.

# Anna said on 10 October, 2013 09:33 AM

Thank you sooo much! After many unsuccessful tries I was considering buying a new scanner but then I found your blog and these instructions! Thank you!!!

# Vinzenz said on 11 October, 2013 11:31 AM

Thank you very much! Worked perfectly for me.

# Richard said on 15 October, 2013 07:59 AM

this wasn't working until I kept scrolling through comments and found someone got it working with CanoScan Toolbox 4.9. It definitely wasn't working with 5.0 so I tried the older toolbox :D. Don't know now whether the path needed to be amended, but as it was already done I didn't bother to go back and take it out. CanoScan Toolbox 4.9 is working as it should with my Canoscan 5200F. Yay!

# Miriam said on 17 October, 2013 09:56 AM

Thank you, I can finally use my trusty old Lide 60 again, so very clear and helpful!!

# Dirk said on 18 October, 2013 08:55 AM

Wasted a few hours before stumbling over your advice here. It worked like a treat. Thanks for passing on the valuable wisdom. Certainly one to remember.

Still a mystery why the path did not get added automatically though. All other devices were fine.

Cheers and keep up the good work.

# Stoyanov, Svetlomir said on 22 October, 2013 09:51 AM

Thanks man, yo're the best :)

# David said on 25 October, 2013 02:36 PM

Thanks for the tip.  You saved another scanner today!  Great job!

# Matthias form Germany said on 26 October, 2013 08:28 AM

Thank you! You saved my day!

# Wiridiana said on 30 October, 2013 06:58 PM

Thank you very much. Works for me now. It's very helpfull.

# BBF said on 31 October, 2013 02:25 PM

Years later and still works! Thanks! You would figure the manufacture would figure this out! W7 64

# Karel said on 06 November, 2013 09:03 AM

Thanks you.

# Chris Grillo said on 08 November, 2013 06:45 AM

This worked fine. The scanner had been working propoerly for two years, then suddenly quit... this fixed it.

# Pat Theo said on 11 November, 2013 02:07 PM

Ah man thanks a million - this is why I love the net

you are a real time saver

All the best man



# Chris S said on 11 November, 2013 08:16 PM

Your fix worked!!!!! Thanks - I have spend many hours reloading programs looking for fixes. Now it works and in Windows 8.1. the screen shots made it so easy to make the changes needed

# Nancy said on 11 November, 2013 10:00 PM

I followed your instructions and now it works.  Thanks so much.  I've had this scanner for a couple of years and this is the first time I've had this TWAIN problem.

# Winfried said on 13 November, 2013 03:52 PM

it woks for the Lide25 too if you adapt the file name to CNQL25 like in the directory.

Thank you so much from Germany and France for this help!

# Arjan said on 14 November, 2013 03:37 PM

For the people who have a Lide30, and this didn't work (like for me):

- Uninstall existing drivers and unplug USB cable

- Copy the Vista drivers contents in the twain32 folder (resulting in C:\Windows\twain_32\CNQL30)

- Plug in the USB cable,

- Stop automatic driver install and browse manually to the twain32 folder

- Do the trick, perfectly described by Jeff

- Open CanoScan toolbox e voila!!! Works!!

Thank you so much for this post, Jeff.

# Robert said on 14 November, 2013 09:32 PM

Today this worked for my LiDE 70.  Thank you so much for this easy fix!

# Andy said on 17 November, 2013 12:14 AM

Incredible. Your instructions were clear and fixed the problem. You're amazing. Thanks a bunch!!

# Nige said on 17 November, 2013 05:28 AM

Huge thanks for your help - I had the same problem and the solution works a treat.

# MC said on 21 November, 2013 03:24 AM

Excellent, thank you

# Michelle said on 21 November, 2013 05:24 PM

WOW.  I thank you for this.  I used this for my LiDE25

MOST IMPORTANT:  don't forget the leading semi-colon.

It is the first time I have been able to use my scanner-to-.pdf file on Windows 7 PRO 64bit!!!!

# theodor said on 22 November, 2013 03:37 PM

man you are a life saver!!!!!!now i have my 4 years old kid  first hand writing saved!!!!!!!!!!!

# Tarquin said on 24 November, 2013 09:56 AM

Many thanks - brought my old scanner back from the dead :)

# Keith Rance said on 24 November, 2013 10:14 AM

Many thanks - Worked for me too. Really clever fix mate!

# Heather said on 24 November, 2013 05:02 PM

Thank you so much for posting this! I've been very frustrated with my scanner. I've just got it working again on this computer after many months! Thanks!

# Alex-IT MAN said on 27 November, 2013 12:09 PM

Jeff-YOU are the man! This info saved me a ton of work and time. thanks a lot and keep up the good work.

# Robert Olson said on 27 November, 2013 10:27 PM

Wow, that was not at all obvious but it worked like a champ with Win 7 Pro and a CanoScan 8400F. Thanks much!

# PaulR said on 02 December, 2013 01:14 PM

Worked perfectly - thanks!

# MartinF said on 02 December, 2013 10:31 PM

Fixed my LiDE 70!  Has been working for years with no problems, must have been the recent MS SQL 2012 Express install that broken the PATH variable?

# ElaineS said on 03 December, 2013 03:54 AM

Perfect! I can now run my LiDE 70 scanner on my new Windows 7 laptop. Thought I'd have to buy a new scanner. Many thanks!

# Mark Schnittman said on 17 December, 2013 10:15 AM

I encountered the exact same problem on Windows 7 Pro. Your path fix worked perfectly. Thanks!

# Dan Gillbjer said on 19 December, 2013 10:45 AM

Thanks, my LIDE50 now operates again on Win7 Pro :)

# Don said on 19 December, 2013 04:31 PM

Thank You!!!

# Sethster said on 26 December, 2013 09:02 PM

Another THANKS Jeff!!!  Hip Hip Hooray!  This fix did the trick on my Canon 8400F Scanner under Win 7 64

# Dave B. said on 30 December, 2013 07:47 AM

Many thanks for solving a most frustrating problem.

# dmj said on 30 December, 2013 04:56 PM

Thanks, worked great!

# Julian said on 01 January, 2014 03:04 PM

Many thanks for this. I had no idea that the "PATH environment variable" even existed. Isn't it a shame that both Microsoft and Canon can't be bothered to mention this on their websites!!!! Anyway, thanks again (I owe you a beer!).

# Jeremy Hawthorn said on 02 January, 2014 11:21 AM

Rather than one other folder, there were 3 folders in my C:\Windows\twain_32. I added all 3 to the path and this did not cure the problem; PhotoStudio 6 still cannot locate my 9000F (II) scanner and gives me the error messages about Twain. How do I determine which is the correct folder to add?

# Iryna said on 02 January, 2014 12:42 PM

Thank you very much! Vielen Dank! Большое спасибо! :)

# Mike said on 06 January, 2014 10:40 PM

Many Thanks it worked with my cannon 8600f. In my case it was  named CNQ4804.  Does anyone know why this happens. Is it caused by Windows updates or new installations?

# Jeremy Hawthorn said on 08 January, 2014 09:16 AM

Further to my posting of 2 January. After setup I could use the scanner with Canon's Scangear, but PhotoStudio 6 could not find the scanner, even after doing all the things recommended above. On a hunch I uninstalled Photostudio and installed it on my laptop. Then, instead of installing the drivers with the CD as Canon strongly advise, I just plugged the scanner into the laptop usb drive, and switched it on. The laptop installed the driver (both machines run Windows7), and lo and behold Photostudio can now contact the scanner. Is this problem a cunning plan on the part of Canon to force everyone to use Scangear? I find Photostudio (which Canon used to supply free with their scanners) a much easier program to use. So: now if I want to scan I have to use my laptop. I can live with that.

# Lena said on 09 January, 2014 08:36 AM

Thank you1 4 years since the post - and it still works!

# Alex said on 11 January, 2014 08:43 AM

That's Amazing! Thanks for the info!

# Kevin said on 13 January, 2014 01:54 PM

Much appreciated. Very clear, very useful.

# Manuel said on 15 January, 2014 03:48 AM

YES. Many thanks.

# Ian said on 18 January, 2014 06:51 PM

Another thank you. Same as most people, Canoscan Lide 70 (O/S WIN 7 64) would not scan from toolbox. Knew it was a software issue as it would scan from Photoshop as a WIA but not Twain, but after that I had no idea. Reinstalling drivers did not work. Your very clear steps fixed it 1st time. Thank you!

# Ben said on 19 January, 2014 08:24 PM

Thanks! Why didn't the Canoscan software put the correct path in the first place? Weird.

# Ted said on 22 January, 2014 03:26 AM

Thanks much!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Smart guy!

# KK said on 07 February, 2014 09:09 PM

Thanks a ton! Works like a charm!

# James said on 09 February, 2014 10:04 AM

Bingo! Dragged out old Canon CanoScan5200F to scan old pictures into personal laptop (IBM T61p) and scan signed contracts into PDF's or work laptop (T410). Got error on T410. Canon support site gleaned nothing, first Google search hit your blog. Thank you very much!!!

# Dieter said on 11 February, 2014 01:06 PM

Thank You!!!!!

Not even the support of Canon was able to help me...

And the Solution is so simple!

They sent me the installation cd's but new install did not help.

Just setting the path, and all is working.


# Ralf said on 13 February, 2014 04:00 AM

Thanks a lot... You saved my day ...

Best wishes from germany !!

(Upgraded XP -> Vista -> W7/32Bit with Canon Lidl25 )

# Juanmi said on 13 February, 2014 05:01 PM

Thanks. that fixed the problem with my Scan Lide 35!

# Erica said on 17 February, 2014 02:17 PM

Fixed it immediately. Thanks for writing this up.

# Theo Gray said on 21 February, 2014 09:12 AM

Thanks Jeff, fixed the problem straight away for my Canoscan Lide 25 (CNQL25) on Windows 7 which was working fine 2 weeks ago and refused to work today.

# Archie said on 21 February, 2014 07:03 PM

Thanks very much Jeff, worked perfectly!!

Greeting from Bangkok

# Adam said on 24 February, 2014 06:12 PM

Thanks so much for taking the time to post this! Perfect solution.

# Paolo said on 25 February, 2014 03:54 AM

Thank you, Jeff!

It works now.


# Richard said on 25 February, 2014 07:30 AM

I've been rescued by this fabulous advice again. This time for CanonScan Lide 25 (I've had to downgrade due to power supply failing on my 5200F and haven't worked out what the problem is yet).

But one tip. My computer has USB2.0 and USB3.0 whereas the Lide 25 is a very old USB lead. Guess what - I couldn't get the toolbox working, until I thought to swap leads with the 5200F. So just be aware of this added complication.

thanks again for saving me!

# Matt said on 27 February, 2014 08:07 AM

Nice one - got my LiDE 500F working on Windows 7 64-bit. Tip: if you don't want to reboot after setting the path variable, open a cmd window and type: path=drive:\dir;%path%

# Russ said on 03 March, 2014 05:11 AM

Thanks!  My scanner (LIDE 25)  was always ready for the bin since I started using Win 7 x64 all those years ago as I always believed it wasn't supported..and now in 2014 I have a solution.  :)

So I can confirm, Win 7 x 64, this advice works!

# koroma said on 05 March, 2014 03:47 AM


# Tony said on 06 March, 2014 05:01 PM


Like so many others I just wanted to add my thanks.

I have a Canon LIDO 600F and after spending hours trying to get it to work on a new Windows 7 x64 machine I finally found your blog which had the answer.

You would think that Canon's Drive installation program would just add the correct Environment Path as part of the install process.

Thanks again

# Nathan said on 06 March, 2014 05:20 PM

Seems like I have a problem with every scanner I connect and I luckily keep finding this solution to my problem.  Works every time.

# Ed Tiley said on 08 March, 2014 03:33 AM


I'm a relieved owner of a Canon LIDE 70.

Like some other folks who have commented, this did not work for me. Ah, but I kept digging. Here's what I managed to do:

1. Went to Control Panel and uninstalled the scanner.

2. Downloaded the driver ( win 7 lide70win641211ea15us.exe ) from the Canon website and saved it to a folder.

3. Right clicked the file and chose Properties | Compatibility. Checked the compatibility box and chose Windows XP.

4. Rebooted. On startup Win 7 installed another driver, and the scanner started humming along.

5. Opened PSP 7 and entered scanner heaven.

FYI, I actually went back and removed c:\windows\twain_32\etc. from the Path variable, rebooted, and the scanner still works!

Hope this helps others,


# Darek said on 09 March, 2014 04:17 PM

Canon Lide 60. I have few different folders inside the C:\windows\twain_32 and one of them are: CNQ4807 and CNQL60. Imagine or not, but adding path to CNQL60 did not work :) so I added path to CNQ4807 too, following instruction and separated by semicolon, and it works !!!

Thanks man, you are the MAN. I have this scanner for years and I love it but I wasn't able to use it on my new notebook. I tried few times and finally give up on it. Today I found this post. Miracle.

# Duder said on 10 March, 2014 12:44 AM

Thanks! Worked great with Windows 8 x64. For Adobe Photoshop CS6 you may need the Twain32 plugin

# Sonja said on 11 March, 2014 08:44 AM

Thank you!!

# Jim said on 13 March, 2014 10:10 PM

Thank you so much! Worked great!

# Wendy said on 14 March, 2014 09:27 AM

This worked for me as well with my Canon 8400F. Thank you so much!

# IT said on 14 March, 2014 09:55 AM

Thanks from Serbia

# Diane said on 22 March, 2014 11:11 PM

Thanks a million!! It WORKED!!!!

# Steve said on 24 March, 2014 01:17 AM

BAM! - You are the man.  Saved me a lot of troubleshooting.  Thank you!!! :)

# Carmen said on 26 March, 2014 06:50 PM

You've saved me from getting insane! Thanks so much!

# Alejandro said on 26 March, 2014 09:05 PM

Thanks, this fixed the problem. Like everyone else, my scanner was working great for years. I didn't use it for a few months and tried to scan a document and suddenly the TWAIN error popped up. After adding the correct path it worked. Feel better now.

# Tom Noble said on 27 March, 2014 05:16 PM

BINGO!  Immediate fix.  Thanks so much!  (No idea where that PATH value went, but it had in fact disappeared...)

# Ulf Strom said on 30 March, 2014 11:40 AM

MANY thanks. Works fine.

# Paxton said on 30 March, 2014 02:24 PM

Just got a new computer and this fixed the issue. Really appreciate the post!

# Lyvie said on 11 April, 2014 01:36 AM

Hi Jeff, thanks for your post, i try this several times but a windows keep appears write unable to open TWAIN source  please check connection then re-start toolbox. i try to add the path which is ;C:\Windows\twain_32\CNQL252 after C:\Program Files\Trend Micro\AMSP\

but it still doesnt work for me, anyone can help please?

# drgogigo said on 13 April, 2014 12:45 PM

Same thing with Cano scan lide 25 and Win7 64. Man U R A GENIUS ! THANKS A LOT.

# ED said on 15 April, 2014 12:41 PM

Jeff Tried it several times double checked everything and still doesn't work. Same problem and response as Lyvie.

We still need help.


# Jack S said on 18 April, 2014 10:20 AM


Periodically I have hit the TWAIN problem but a reboot fixed it. Today after 3 reboots I was still unable to get the scanner working. Same TWAIN problem that you reported. I tried adding CNQxxxx to the PATH variable and now the scanner is working perfectly.

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