Objective: The aim of this study was to evaluate the degree of psychological problems Iranian children and adolescents have, using parent report form of the Strengths and Difficulties Questionnaire (SDQ). Methods: In a community-based study, 9636 children and adolescents aged 6-17 years were selected using the multistage cluster random sampling method from five provinces of Iran: Tehran, Isfahan, Fars, Razavi Khorasan and East Azerbaijan. The parents completed the SDQ, which consisted of five subscales including emotional problems, conduct problems, hyperactivity, peer problems and prosocial behaviors. Result: The results revealed 21.4% of emotional problems, 32.9% of conduct problems, 20% of hyperactivity, 25.6% of peer problems, 7.6% of problems in prosocial behaviors and 16.7% of total difficulties among Iranian children and adolescents. We found that emotional problems were more prevalent among girls, while conduct problems, hyperactivity, total difficulties and problems in prosocial behaviors were more prevalent among boys. High educational level of parents was a protective factor against some psychological problems. Conclusion: Considering the proportion of psychological problems in Iranian children and adolescents, we need to develop and implement special policies and programs to provide appropriate mental health services.