OBJECTIVE: To investigate the prevalence of attention deficit hyperactivity disorder (ADHD) and behavior problems among school-age children in Shenzhen City of Guangdong. METHODS: A total of 10553 students in Grades 1-6 from different primary schools in Shenzhen City were assessed by Conners Parent Symptom Questionnaire (PSQ) and Conners Teacher Rating Scale (TRS). Children showing abnormalities according to PSQ or TRS were further assessed according to the diagnostic standard for ADHD as laid out in the diagnostic and statistical manual for mental disorders- 4th edition (DSM-Ⅳ). RESULTS: A total of 8193 PSQ and TRS assessments were completed. The children were aged from 7 to 13 years. The total prevalence rate was 7.60% by PSQ and 5.59 % by TRS. Four hundred and forty-two children were diagnosed having ADHD by DSM-Ⅳ, with a prevalence rate of 5.39%. There were significant differences in the prevalence rate of ADHD among children aged 7 to 13 years (χ2=21.613, P<0.05). In children aged 7 to 9 years, the prevalence rate was higher (above 6%). The prevalence rate of ADHD in boys was significantly higher than in girls (6.65% vs 3.12%; P<0.05). Impulsion and hyperactivity (79.6%), learning (60.6%) and conduct disorders (52.0%) were the main behavioral problems in children with ADHD. The prevalence of learning disorders was higher in girls than in boys. Conclusions The prevalence rate of ADHD in children from primary schools in Shenzhen City is 5.39 %, and it is higher in children aged 7 to 9 years. Boys have a higher prevalence rates of ADHD than girls. Impulsion and hyperactivity, learning and conduct disorders are common problems in children with ADHD.