Anecdotally and empirically, there is clear evidence that children with the Combined subtype of Attention-deficit/Hyperactivity Disorder (ADHD) experience disturbed peer relations, yet the field has not clearly established the origin of these difficulties. This is the first known investigation to examine the role of peer entry as a means to determine the social competence of boys with ADHD as they joined lab-based games played by age-mates who were good friends but unfamiliar with entry boys. Observational data of entry boys and their hosts, plus coders' ratings, indicate that 7- to 12-year-old boys with and without ADHD did not differ in the use of competent entry strategies known to lead to acceptance from peers. However, boys with ADHD relied more heavily on incompetent entry strategies (e.g., disruptive attention-getting) known to exacerbate negative peer reputation. In addition, they failed to apply a frame-of-reference that was relevant to host boys' ongoing activity. As such, host boys considered boys with ADHD less likeable as they spent more time with them. This pattern of findings has theoretical implications and informs the foci of social skills interventions for children with ADHD.