Cognitive performance was examined in 145 thirteen- to sixteen-year-old adolescents for whom prenatal exposure to marihuana and cigarettes had been ascertained. The subjects were from a low-risk, predominantly middle-class sample participating in an ongoing, longitudinal study. The assessment battery included tests of general intelligence, achievement, memory, and aspects of executive functioning (EF). Consistent with results obtained at earlier ages, the strongest relationship between prenatal maternal cigarette smoking and cognitive variables was seen with overall intelligence and aspects of auditory functioning whereas prenatal exposure to marihuana was negatively associated with tasks that required visual memory, analysis, and integration. The interpretation of the results is discussed in terms of the differential observations related to in utero exposure to cigarettes and marihuana and the nature of the cognitive variables associated with the two drugs.