Attention Deficit Hyperactivity Disorder (ADHD) is the most common psychiatric disorders, and lack of attention to treatment may cause a harmful effect to a patient and his/her family. This cross-sectional study was carried out on 1200 (604 boys and 596 girls). Questionnaire for parents and teachers were used to confirm and evaluate the prevalence of the disorder. From the sampled students, 67 individual (6.5%) suffered from ADHD. There was a significant relationship between the prevalence of the disorder and variables such as birth order and parents education, but prevalence of the disorder was not related to the type of delivery, parents smoking, pre-terming of child, history of head trauma and parents occupation. The quality of children life and adverse effect on individual and social life, screening and treatment in primary school's students are necessary. This study aimed to evaluate the prevalence of this disorder in primary school's students in Khorramabad.