RESUMEN
The present research was conducted to study the effect of play therapy on reducing behavioral problems of children with oppositional defiant disorder. Using multistage cluster sampling, regions 6, 7, and 8 in Tehran were selected. Among kindergartens of these areas, 3 kindergartens which were supported by the welfare organization were randomly selected. Of all pre-school children of these 3 kindergartens, 40 children who could have behavioral disorder, according to their teachers and parents, were carefully tested. Of them, 16 children who showed severe symptoms of oppositional defiant disorder, were selected, via the results obtained from child symptom inventory questionnaire [CSI-4], teacher's form, and a researcher-made self-control checklist. Then, the subjects were randomly divided into one control and one experimental group. This research is quasi-experimental, and is conducted using of pre-test, post-test, and control group. Values of calculated F for oppositional defiant disorder in control group and experimental group was meaningful after fixing the effect of pre-test [P<0/001]. Therefore, a meaningful difference existed between the means of post-test scores of disobedience disorder in the experimental and control groups through the fixed effect of pre-test effect. Comparison of adjusted means of 2 groups shows that the mean of attention-deficit hyperactivity disorder [ADHD] in experimental group was lower than control group. Therefore, applying play therapy reduced severity of ADHD in those children in experimental group compared to those in control group who did not receive such instructions. Results of this research demonstrates that children's disobedience can be reduced by play therapy