Volumes of cerebral gray and white matter were measured in 22 children with neurofibromatosis type 1 (NF1) and in 20 controls. Judgment of Line Orientation (JLO) and the Developmental Test of Visual-Motor Integration (DTVMI) were administered to 16 of the NF1 patients. General linear models analysis of covariance revealed significantly larger brain volumes in NF1 children than in controls, particularly in white matter, and particularly in girls. JLO and DTVMI performance were positively related to right-hemisphere gray-matter volume. The results implicate a failure of growth control in NF1, leading to aberrant neurodevelopment. Our findings also suggest a basis for refined understanding of learning disabilities, which are a prominent feature of NF1.