We evaluated 32 nonmedicated male adolescents diagnosed with attention-deficit/hyperactivity disorder (ADHD) in childhood, 35 male adolescents similarly diagnosed who were receiving methylphenidate (MPH), and 77 control boys. Both ADHD groups completed self-report questionnaires assessing sleep disturbances; weekday and holiday sleep duration; and symptoms of ADHD, anxiety, and depression. Parents and teachers rated the severity of the participants' ADHD. The control group completed self-report questionnaires assessing sleep disturbances. We found that nonmedicated participants and controls did not differ in the severity of sleep disturbance. In contrast, the medicated participants demonstrated a significantly greater severity of sleep disturbance compared with the nonmedicated participants and reported elevated levels of symptoms of ADHD, anxiety, and depression. Specific analyses showed that depressive symptoms contributed significantly to the degree of sleep disturbance when controlling for ADHD diagnosis and MPH treatment. These findings suggest that among adolescents with ADHD symptoms, the severity of symptoms of depression may contribute to the degree of sleep disturbance in addition to the effect of their primary disorder and MPH treatment.