Adolescent development is associated with progressive increases in the ratio of cerebral white-to-gray matter volume, but it is unclear how these changes relate to cognitive development and whether they are associated with sex-specific variability in cerebral maturation. We examined sex differences in the relation between cerebral tissue volume and cognitive performance in 30 healthy adolescents (ages 13 to 17 years using morphometric magnetic resonance imaging (MRI). In the 10 boys, greater white matter volume during adolescence was positively correlated with faster speed of information processing and better verbal abilities, while cerebrospinal fluid volume was negatively correlated with verbal abilities. No significant relations between cerebral tissue volume and cognitive abilities were found for the sample of 20 girls, raising the possibility of a different developmental trajectory for females that was not sampled in the age range of this study. Findings suggest sex-specific developmental differences in the relations between cerebral structure and function.