People with attention-deficit/hyperactivity disorder (ADHD) are affected by the disorder throughout their lifetimes. Children with ADHD often have comorbid oppositional defiant disorder and conduct disorder in addition to having developmental and social problems. The persistence of ADHD into adolescence and young adulthood varies according to who is being interviewed and the criteria used to define the disorder. For those adolescents and adults in whom ADHD does persist, educational difficulties continue, and problems in the areas of employment, driving, and sexual relationships emerge. ADHD is also associated with increased health care costs even when controlled for psychiatric treatment. Because most ADHD research has been conducted with male children and adolescents with ADHD, combined type, most outcomes for ADHD should be thought of as male outcomes for this subtype. In the future, ADHD researchers should study outcomes for girls and women and for people with ADHD, predominately inattentive type.