Children with emotional and behavioural difficulties (EBD) and those who also have developmental disorders, such as attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder (ASD), can experience the same adverse consequences in their peer interactions and relationships. This present study compared the emotion regulation and peer relationships of children aged 8-12 years ("M" = 9.86 years, SD = 1.49) with EBD ("N" = 33) and children with EBD plus a diagnosed developmental disorder ("N" = 28). Multivariate analysis of variance (MANOVA) with Bonferroni adjusted alpha levels revealed no significant main effect for emotion regulation according to EBD status. There was, however, a multivariate main effect for sex, with females presenting with higher levels of negative emotional intensity (e.g., frustration, anger, aggression) than males. A second MANOVA revealed no significant main effect for peer relationships according to EBD status and sex. Significant correlations revealed that the EBD-only group experienced greater adverse peer interactions than the EBD-plus-developmental disorder group. These findings are important for educators and researchers involved in the development and evaluation of prevention and intervention programms for children with EBD.