Boys identified as hard-to-manage at age 4 and age-matched controls were assessed on laboratory measures of inattention, impulsivity, and hyperactivity at ages 4, 6, and 9. Hard-to-manage boys still exhibited some behavioral difficulties at age 9, but were not more inattentive or impulsive than controls. Boys with Attention Deficit Disorder (ADD) at age 9 showed performance deficits in each symptom-related domain relative to problem boys without ADD and controls. However, hard-to-manage problem boys with and without ADD did not differ on most earlier measures of inattention, impulsivity, and hyperactivity, suggesting that symptoms specific to ADD emerged more clearly between ages 6 and 9.