This study investigated the association of a performance-based measure of executive functioning (EF) with academic, social, and behavioral performance ratings in a convenience sample of 153 children aged 5 to 12 (78% male, 83% Caucasian) diagnosed with attention-deficit/hyperactivity disorder (ADHD). Multivariate regression showed that above and beyond age and ADHD severity, poorer EF performance was uniquely associated with more impairment in reading, written expression, and math by teacher report, and more impairment in the overall school and reading domains by parent report. ADHD symptoms were more strongly associated with ratings of impairment in social relationships, organized peer activities, and classroom behaviors than EF performance. Age did not moderate the findings, but younger children were rated as having more trouble with participation in organized activities by parents, as more likely to disrupt class by teachers, and to have problematic relationships with peers by parents and teachers. EF and academic performance appeared worst in the groups seen as highly symptomatic and impaired by both parents and teachers, and by teachers only. EF deficits may be a specific risk factor for academic impairment in children with ADHD.