In this national sample of 3082 children, 8.7% met criteria for attention-deficit/hyperactivity disorder (ADHD), half of whom had the inattentive type. Children in the lowest income group were twice as likely to have ADHD as those in the highest income group and were 3-fold more likely to have the hyperactive-inattentive type. Only about half of the children who met criteria for ADHD had received that diagnosis from a physician in the prior year, and only one-third of these children had consistent medication use. Poorer children used the least medication. These findings suggest that diagnosis and treatment of ADHD, especially in poor children, must be improved.