Previous research has shown sex differences in brain morphology (De Bellis et al., 2001). However, these studies have not taken gender into account. Gender is a phenotype that describes behavior. In this study, we examined the relationship between gender, sex, and brain volumes in children. One hundred and eight children ages 7 to 17 were administered the Children's Sex Role Inventory (Boldizar, 1991) and obtained volumetric brain data via magnetic resonance imaging (MRI). We found that, in the frontal lobe, higher masculinity predicted greater volumes of white matter. Also, in the temporal lobe, higher femininity predicted greater volumes of gray matter.