The performances of 20 children with attention deficit hyperactivity disorder (ADHD) were compared with those of 20 matched normal controls on a battery of neuropsychological tests. The ADHD children exhibited impaired function in reading comprehension, verbal learning and memory, and on the Information, Arithmetic, Digit Span, Block Design, and Coding subtests of the Wechsler Intelligence Scale for Children-Revised, but they performed nearly normally on measures of verbal and design fluency and on the Wisconsin Card Sorting Test. The hypothesis that disturbances in frontal lobe function related to impulse control may be responsible for the cognitive impairments observed in ADHD was not supported. Inability to control and direct attention appears to be more central to the pathophysiology of this disorder.