I am not in college today, but aboout 4 years ago I was. I went to San Francisco State. It was a major challenge to go through the process of qualifying for disability services and took several months. Most of the services didn't fit my needs. The only ones that held promise were psychological counceling (available to all students) and going into the disabilities office frequently for pep talks and help organizing my time.
I think it varies from college to college, and even then, from program to program within a particular college. I work at a community college in the Midwest, and we do pretty well supporting students w/ disabilities, including ADHD. However, there are some departments that are less cooperative than others. I know I cringe when one of my students has to deal with particular instructors because I know from history how little they bend. But overall, I'm pretty proud of what we provide our students. There's a state university 10 miles down the road. I hear that overall, they are much less supportive than we are, but a friend who has LD and ADHD and several medical problems was able to get thru and found her dept. fairly accomodating.
If you are checking out schools, I would recommend some very specific, pointed questions and a f2f visit.