We compared social self-competence ratings in 9-12 year old girls with (n = 42) versus without (n = 40) ADHD, relative to ratings of the girls' social competence made by mothers, teachers, and blind raters during a social laboratory task. Relative to scores from mothers, teachers, and the lab-task, girls with ADHD over-estimated their competence significantly more than control girls. Over-estimates were greater for girls with ADHD who also had heightened oppositional-defiant symptoms, or lower depressive symptoms. Over-estimates were positively related to a socially desirable reporting bias for girls with ADHD, but not for control girls, suggesting that girls with ADHD attempt to present themselves in an unduly positive, self-protective light. For girls with ADHD, over-estimates also were positively related to maladjustment and negatively related to adjustment. However, for girls without ADHD, over-estimates were positively related to adjustment. Overall, over-estimates of competence function differently in girls with and without ADHD.