lucablue wrote: No!

images are larger (not thumbnail, the full-size)

Try and upload a new one and see if that resizes - if it does this means that someone changes the configuration settings after the images were already uploaded.

lucablue wrote: No,
I'm the only administrator. Moreover when I've changed the dimensions I've tried to upload a bigger image and it resize.

But when any user register to the website it seems not work.

Please try new test and give back results:

1. original size of image being uploaded?
2. size of uploaded image in images/comprofiler folder
3. configuration parameters in yoru CB -> COnfiguration -> Images tab

lucablue wrote: Ok,
I've taken a big image (4000x3000) and upload with one of my existing user.
CB has correctly resized.

So the problem seems with new registrant.

I would be surprised.

Test with a new registration - you should get same results.