Background The catechol-O-methyltransferase (COMT) gene codes for an enzyme that degrades prefrontal cortex (PFC) synaptic dopamine. Of two identified alleles (Met and Val), the Met allele results in COMT activity that is up to 4 times less pronounced than that conferred by the Val allele, resulting in greater PFC dopamine concentrations. Met-Met homozygotes perform better than individuals who possess the Val allele on PFC-mediated cognitive tasks. These genotypic variations and their associations with executive functions have been described in adults and prepubescent children, but there is a paucity of research assessing these relations in adolescent samples. Methods In this study, 70 children aged 9–17 were genotyped for COMT and completed measures of working memory, attention, fine motor coordination, and motor speed. Results COMT genotype modulated all but the motor speed measures. The Val-Met genotype was optimal for performance in this adolescent sample. Conclusions Results are discussed within the context of developmental changes in the dopaminergic system during adolescence.