Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
My professor sometimes asks me to referee papers for him.
Should I list the corresponding journals in the professionals activity section of my CV?
Yes, if your professor explicitly lists you as a reviewer or sub-reviewer with the program committee of the conference/journal; no if your review is then edited by your professor before submission.
Yes. It is the very prototype of service to the professional community that you want to show that you are willing to perform.
The question that Scrooge linked to has good advice for how to do so.