This research attempted to test D. R. Lynam's (1996) hypothesis regarding the developmental relation between adult psychopathy and children with symptoms of hyperactivity, impulsivity, and attention problems (HIA) and concurrent conduct problems (CP). In a large sample of adolescent boys, 4 groups (non-HIA–CP, HIA only, CP only, and HIA–CP) were compared on measures found to discriminate between psychopathic and nonpsychopathic offenders. In line with predictions, the HIA–CP boys most closely resembled psychopathic adults. HIA–CP boys scored higher than HIA-only and non-HIA–CP boys on a measure of psychopathic personality. As with their adult counterparts, HIA–CP boys were the most antisocial, were the most disinhibited, and tended to be the most neuropsychologically impaired of all the groups. Implications for treatment, research, and the study of comorbidity are discussed.