Attention-deficit/hyperactivity disorder (ADHD) persists into adulthood in an increasingly recognized number of individuals with childhood onset. The symptoms of adult ADHD are similar to the restlessness, distractibility, and impulsivity central to childhood ADHD, but expression of symptoms changes as the individual matures. A childhood history of ADHD is requisite for a diagnosis of adult ADHD, although full DSM-IV criteria for the childhood disorder need not be met as long as significant symptoms and impairment occurred. Three case reports described here illustrate the migration of symptoms and the use of retrospective reporting and rating scales to determine a diagnosis of adult ADHD. These reports also stress the high probability of comorbid disorders and family aggregation of ADHD, as well as the likelihood that the adult with ADHD has developed coping mechanisms to compensate for his or her impairment.