Previous studies of individuals with Sturge-Weber syndrome have focused on the medical aspects of this syndrome, but little has been known about the affective and behavioral correlates. We collected psychological and medical data from parents and teachers for 79 children and adolescents with Sturge-Weber syndrome and a group of their siblings. We also obtained the results of intellectual assessment for a subset of the Sturge-Weber syndrome group. The young people with Sturge-Weber syndrome exhibited more problems than the group of siblings across a number of behavioral domains: intellectual/academic, social skills, mood, and compliance. Those children most at risk for psychological problems were those with lower levels of intellectual functioning, those with seizure disorders, and those with more frequent seizures. Larger port-wine stains were also associated with an increase in mood and social problems but only for older children. Increased age was not associated with lower levels of intellectual or academic functioning, but mood and social problems were more common in older children.