The present study examined the effects of stimulant medication on the self-evaluations of and attributions for task performance of 26 attention-deficit hyperactivity disordered boys. Each boy performed a continuous performance task twice, once while on medication and once while on placebo. Immediately following the completion of the task, the boys were asked a series of questions concerning their self-evaluations of, and attributions for, their performance. Two findings of note were obtained. First, medication, compared with placebo, increased the correspondence between the boys' self-evaluations and their performance. Second, the boys did not use medication as a frequent explanation for their performance, as others have predicted. In fact, the boys picked medication as an explanation for their successes significantly less often than either effort or ability.