Stigma research suggests that exclusion of peers with mental health problems is acceptable, however, no research has explored young people's beliefs about the fairness of exclusion. Group interviews with 148 adolescents explored judgements about the fairness of excluding peers with ADHD or depression from dyads and groups. Young people evaluated exclusion of peers with ADHD or depression from dyads and groups, with the exception of group exclusion of the peer with ADHD, as mostly unfair. Beliefs about the fairness of exclusion were influenced by the attributions that they applied to the target peer's behaviour, social obligations and loyalty within friendships and concerns about the adverse psychological effects of exclusion. Furthermore, their evaluations were influenced by personal beliefs about the social and personal costs of including the target peer. Evaluations of exclusion highlight novel avenues for to develop knowledge on the stigma of mental health problems. (C) 2015 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.