This study is part of other ongoing studies of individuals with ADHD. The study participants have already undergone neurobiological measurements, particularly magnetic resonance imaging (MRI) of the brain, through other research studies. As a follow-up to these studies, participants will next undergo psychiatric interviews, neuropsychological tests, and another MRI. In addition to the clinical evaluation of the participants, further research will be conducted on the genetics of ADHD. These genetic studies will evaluate people with ADHD as well as their family members and a control group of healthy people.