Background: Research suggests that children's reactions to peers with mental health problems are related to the maintenance and outcomes of these problems. However, children's perceptions of such peers, particularly those with internalising problems, are neither well researched nor understood. The present study aimed to test a series of models relating socio-demographic and attributional variables to the acceptance of hypothetical boys and girls with attention deficit hyperactivity disorder (ADHD) and depression. Methods: A sample of 595 participants, drawn from five different age-groups spanning early childhood to late adolescence, completed a booklet of questions in response to two vignettes describing the behaviour of hypothetical target peers with depression and ADHD. The sample was drawn from schools randomly selected in the east of Ireland. Results: The models indicated that age and gender of the participant, and the perceived responsibility of the target character for his/her condition, were the three most important predictors of acceptance in all models. However, the relationship between these variables and acceptance varied depending on the gender of the target child and the condition (depression or ADHD) in the models tested. Conclusions: The findings of the study suggest that the relationships between socio-demographic and attributional variables and acceptance of peers with mental health problems depend on the type of mental health problem under consideration. The findings have implications for the development of information and education programmes to improve the integration of children with mental health problems.