Friendship formation (making friends, keeping friends, and having successful interactions with peers and adults) constitutes a critical developmental-social milestone for adolescents. This process can be especially challenging for adolescents with attention-deficit/hyperactivity disorder, whose attentional problems may negatively affect their social skills (verbal and nonverbal language) and who fail to appreciate the complexity and nuances of adolescent communication. They often do not respond to feedback cues. They may be perceived as "immature," lacking empathy, and loners and losers, they may endure a "reputational bias," and they often experience coexisting challenges (eg, language problems, learning disabilities, or obesity). Successful and gratifying interactions, or the lack thereof, deeply and broadly affect adolescents: their self-esteem, self-image, confidence, school-learning, lifestyle, behavior, sexual activity, intimacy formation, mental-emotional well-being, and physical health. Successful achievement of this ever-evolving milestone has lifelong implications. This article describes various social-interactional skills, other components of social competence, and the dysfunctions that may cause social failure and suffering and describes how to evaluate and help manage problems in adolescents with attention-deficit/hyperactivity disorder.