OBJECTIVES: Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common neurobehavioral disorders of childhood, which interferes with the social and educational development. This study aimed to determine the prevalence of ADHD among primary school children in Al-Qalyubia Governorate, Egypt, to identify underlying factors related to ADHD and to recommend a prevention and control program for this disorder. METHODS: A cross-sectional study was conducted on 921 students, aged 6-12 years, from four primary schools in Al-Qalyubia Governorate. ADHD was assessed using screening scales for teachers and parents. Underlying risk factors were investigated using a structured questionnaire filled by parents. RESULTS: The prevalence of ADHD among primary school children was 21.8% and 16.2% based on the teacher and parent scales respectively. The increased risk of ADHD was associated with child exposure to punishment, irritable parents’ relation, poor parent-child relationship, watching TV, cyanosis and head trauma. ADHD was more likely in children with parental consanguinity and whose mothers were exposed to passive smoking during pregnancy. ADHD was less likely in urban children from high socioeconomic level. CONCLUSIONS: ADHD presents a troublesome problem among primary school children. Collaborative efforts are required to control risk factors associated with ADHD and to decrease its prevalence.