Background and purpose: Present study aimed to investigate the efficacy of cognitive behavioral therapy on the reduction of aggression in preschool children with attention deficit/Hyperactivity Disorder.

Method: Current research was a quasi-experimental study with pretest-posttest control group. The study population consisted of all the four to six years old preschoolers who registered in the kindergartens of Rasht City in 1391-92 academic year. The sample consisted of 400 preschoolers who were selected using random multi-stage cluster sampling method, and completed Child Symptom Inventory 4 (CSI-4). Then, 30 children with attention-deficit/hyperactivity disorder were selected and randomly assigned to experimental (N= 15) and control (N= 15) groups and completed Preschoolers Inventory of Aggression. Experimental group received a 10-session cognitive behavioral therapy (1-hour/ 2 sessions per week), while control group received no therapy. Participants completed posttest after therapy sessions.

Results: The results of covariance analysis showed that cognitive behavioral therapy had significant impact on the reduction of aggression.

The obtained results through covariance analysis showed that teaching play therapy based on cognitive behavior approach can lead to reduction of aggression significantly.

Conclusion: In play therapy, children have the opportunity to show their accumulated frustrations via aggression in an appropriate context, and learn and internalized sufficient ways to control this aggression.