This study explores the social impact of ADHD, with and without opposition-defiant behaviour (ADHD+ODD (n = 22) and ADHD-only (n = 18)), in 9- to 12- year old girls compared to girls without ADHD (n = 40). Girls played a computer game involving simulated players, and mothers and teachers completed rating scales. In general, mothers and teachers saw girls with ADHD+ODD as more overtly and relationally aggressive and less prosocial than girls with ADHD-only, who were seen as more overtly and relationally aggressive and less prosocial than control girls. On the computer game, girls with ADHD+ODD were more overtly aggressive, more directly relationally aggressive, and showed less skilled behaviour than the other groups. Girls with ADHD-only showed less covert, indirect relational aggression and more socially awkward interactions than girls in the control group on the computer game. In all, the results indicate that girls with ADHD, with and without ODD behaviour, engage in socially detrimental behaviours.