The purpose of this research was to investigate the relationship between recent and long term substance use on adolescents' neuropsychological functioning. Subjects were 77 adolescents who were referred for outpatient treatment for drug and conduct problems. Subjects were administered the Luria-Nebraska Neuropsychological Battery-III, structured interviews to assess substance use, and urine tests. Subjects were divided into neuropsychologically impaired and nonimpaired groups. Results indicated no significant group differences for: self-reports of lifetime use of alcohol, cannabis, and hard drugs; self or collateral reports of recent (past 30 days) use of alcohol, cannabis, and hard drugs; or urinalysis detection of alcohol, cannabis, and hard drugs. Correlations between these dependent measures of substance use and neuropsychological functioning were also nonsignificant (all ps >. 05). Although neuropsychological impairment was observed for some subjects in this sample, it was unrelated to their cannabis, hard drug, or alcohol use. These results are consistent with those found in the adult literature, given the relatively short period of time that these youth have used such substances. However, given the severity of their absolute levels of substance usage, they may be at greater risk for developing future neuropsychological problems, related directly to the ingestion of alcohol and illicit drugs, and to their secondary effects (e.g., head traumas, malnutrition).