It probably won't hurt you, but law school admissions is almost ALL about numbers. You can see this by looking at lawschoolnumbers.com. It won't hurt you to submit it, but schools are not likely to have much sympathy for an ADHD diagnosis. They really don't have much sympathy in admissions period unless your story is newsworthy i.e. lost your arm jumping on a grenade to save 20 orphans in Africa or something like that. All schools claim to "care" about soft factors, but they really don't unless it is something like the example above. I would check out lawschoolnumbers.com to see what your chances are at particular schools.