INTRODUCTION:The world prevalence of ADHD ranges between 5-10%. The prevalence in Israel was generally studied from prescriptions of methylphenidate and not from cohorts of children. METHODS:We assessed the prevalence of ADHD among a cohort of early school age children in the Jewish and Arab populations using DSM-IV criteria and evaluated the difference between teachers' and parental assessment. We also studied in the Jewish population the differences in several social-behavioral parameters between children with and without ADHD. RESULTS:The rate of ADHD among the Jewish children was 9.5% and among the Arab children it was significantly lower - 7.35%. Teachers' evaluation in the Jewish population was 2.3 times higher than parental evaluation but in the Arab population it was closer to that of the parents, being only 12% higher. In addition, there were more regulatory, behavioral and learning problems among the Jewish children with ADHD compared to children without ADHD. CONCLUSIONS:The rates of ADHD in school age children among both Jews and Arabs fall within the average rate in other countries. The high difference between teachers' and parental assessment of ADHD in the Jewish population emphasizes that ADHD diagnosis should rely on the joint behavioral assessment of both. The prevalence of ADHD in Jewish early school age children is slightly higher than in Arab children and the inattentive type is the most common. There is a discrepancy between teachers' and parents' evaluation of children's behavior in the Jewish population, but this discrepancy is less in the Arab population.