Objectives : A higher level of aggression has been reported for children with attention-deficit/hyperactivity disorder (ADHD) than for non-ADHD children. Aggression was shown to have a negative effect on the social functioning of children with ADHD. The ability to recognize facial emotion expression has also been related to aggression. In this study, we examined whether impulsivity and dysfunctional recognition of facial emotion expression could explain the aggressiveness of children with ADHD. Methods : 67 children with ADHD participated in this study. We measured the ability to recognize facial emotion expression by using the Emotion Recognition Test (ERT) and we measured aggression by the T score of the aggression subscale of the Child Behavior Checklist (CBCL). Impulsivity was measured by the ADHD diagnostic system (ADS). Results : The teacher rated level of aggression was related to the score of recognizing negative affect. After controlling for the effect of impulsivity, this relationship is not significant. Only the score of the visual commission errors ex plained the level of aggression of children with ADHD. Conclusion : Impulsivity seems to have a major role in explaining the aggression of children with ADHD. The clinical implication of this study is that effective intervention for controlling impulsivity may be expected to reduce the aggression of children with ADHD.