Adolescents with attention-deficit/hyperactivity disorder (ADHD) obtain less sleep than their typically developing peers. Observational studies indicate that inadequate sleep is correlated with impairment in adolescents with ADHD, but it remains unknown if sleep is causally related to impairment. This study will use an experimental sleep restriction and extension protocol to evaluate sleep as a contributor to clinically significant impairment and possible target for intervention in adolescents with ADHD.