This article reviews research conducted over the past 20 years on the social competence of children with Attention Deficit Hyperactivity Disorder (ADHD). A substantial body of research suggests that children with ADHD experience significant interpersonal difficulties. The social competence of ADHD children is considered using three indices: typical social behaviours or social functioning, internal cognitive structures relating to the behaviours, and the products or outcomes of their social functioning. Possible mechanisms underlying their interpersonal difficulties are discussed. The article concludes by outlining the significance of these difficulties for later life outcomes, and emphasising the importance of uncovering the mechanisms by which these difficulties arise.