Few studies have comprehensively examined possible gender differences in the school functioning of children with attention deficit hyperactivity disorder (ADHD). This study investigated differences in academic, social, and emotional and behavioral functioning between 133 male and 42 female elementary school students who met research diagnostic criteria for ADHD. School functioning was assessed using teacher ratings, direct observations of classroom behavior, and a standardized, norm-referenced achievement test. Results indicated that participants, regardless of gender, experienced impairment across all functioning domains. The few gender differences obtained varied across areas of functioning and were dependent, in part, on the type of score and comparison group used. Specifically, although girls were less likely to have ADHD than were boys, when they did exhibit this disorder, their impairments were as severe, or possibly more severe, than for boys relative to non-ADHD peers of the same gender. Implications of these findings for school-based practice and research are discussed. (Contains 3 tables and 1 footnote.)