This study examined the direct association between Attention Deficit Hy- peractivity Disorder (ADHD) symptoms (i.e. inattention and hyperactivity symptoms) and children's experience of best friend conflicts, and the mediating role of aggression, emotional and behavioural instability, exploring possible gender differences. The sample consisted of 334 children (52 % female; Mage=9.38, SD=0.89) attending primary schools in northwest Italy. ADHD symptoms were measured with a question- naire completed by teachers whereas others variables were assessed a self-report questionnaire completed by the children. Analyses revealed that inattention and hyper- activity symptoms were differently associated with best friend conflicts according to gender. Among boys, only hyperactivity symptoms were associated with best friend conflicts whereas among girls only inattention symptoms contributed to best friend conflicts. Aggression and emotional and behavioural instability were found to mediate these associations for both genders. These findings suggest that to understand fully the association between ADHD symptoms and best friend conflicts it might be helpful to consider the different manifestations of that association by gender, whilst also consid- ering behavioural and emotional dimensions of children's psychosocial adjustment.