Background and Aim: attention-deficit/hyperactivity disorder or ADHD is one of the most common problems of children and adolescents and the reason for referral to psychiatrists and psychologists. Therefore, the aim of this research was to the effectiveness of parent-child interaction training on behavioural problems and aggression of children with ADHD symptoms. Methods: In terms of the purpose, the current research design was of an applied type and in terms of the method of conducting it, it was a quasi-experimental research with a pre-test, post-test and two-month follow-up plan with the experimental and control groups. The statistical population of this study consisted of 6-10-year-old children with ADHD who were referred to a private counselling centre in the 10th district of Tehran in 1401. An available sampling method was used for sampling, and 30 people were selected, and 15 people were equally assigned to the experimental group and 15 people to the control group. In this research, the tools used included Achenbach's Child Behavior Checklist (CBCL), and Buss & Perry's (1992) Aggression Questionnaire. Parent-child interaction therapy was performed according to McNeil & Hembree-Kigin's (2010) protocol on the experimental group, but the control group did not receive any intervention. Statistical data was analyzed with spss software and using analysis of variance with repeated measurements, and Bonferroni's post hoc test was used to check the stability of the effects of the interventions. Results: F values were calculated for behavioural problems (F = 7.63) and aggression (F = 10.74). It can be concluded that the effect of the group membership factor, or in other words, the treatment of parent-child interaction, has led to a significant decrease in dependent variables (p<0.01). The results of Benferroni's post hoc test indicate that the effect of parent-child interaction therapy on behavioural problems and aggression of children with ADHD was stable. Conclusion: It can be concluded that parent-child interaction training was effective on behavioural problems and aggression of children with ADHD symptoms, and this effect was stable.
