The purpose of this study was to investigate the self-perception bias (SPB) in adolescents with attention-deficit hyperactivity disorder (ADHD). The SPB was defined as adolescent underestimation of their learning and behavior problems in comparison to parent- or teacher-reports or a standardized achievement test. The sample comprised 74 adolescents, ages 13 to 18 (40 ADHD; 34 comparison). Compared to adolescents without ADHD, adolescents with ADHD underreported their symptoms and impairment when parent-reports, but not teacher-reports were the indicator of performance. Adolescents with ADHD, however, reported more difficulties in all areas of functioning than adolescents without ADHD. In the sample of adolescents with ADHD, self- and parent-reports of learning problems, but not teacher-reports, were significantly associated with adolescent total academic achievement test score. Adolescents with learning problems as measured by the achievement test, and social problems as rated by parents, reported higher levels of these difficulties than adolescents whose functioning was in the average range; however, adolescents with clinical levels of oppositional behaviors, as rated by parents or teachers, did not report elevated levels of these behaviors. Depressive symptoms were associated with a lower SPB. Implications of these findings for psychologists' use of self-report measures with adolescents with ADHD are discussed.