To evaluate the prevalence of ADHD, comorbidity rates with Disruptive Behavior Disorders (DBD), and main negative outcomes in primary-school students in Nampula, Mozambique. We selected a random sample of 748 students for ADHD screening from a population of around 43000 primary school students. The Swanson, Nolan, and Pelham Rating Scale version IV (SNAP-IV scale) was applied to both parents and teachers. All positive screened students (n = 76) and a propensity score-matched random subset of negative screened subjects (n = 76) had a psychiatric evaluation carried out by a child psychiatrist. The prevalence of ADHD was estimated to be 13.4% (CI95%: 11.5%-19.2%) and 30.6% of youths with ADHD presented a comorbid DBD. Students with ADHD (n=36) had significantly higher rates of both substance use (alcohol, marijuana) (p < .001), and school repetitions than controls (n=96; p < .001). Comorbidity between ADHD and DBD increased the chance of substance use (p < .001). Secondary analyses, using more restrictive ADHD diagnostic criteria determined a lower prevalence rate (6.7%; CI95%: 5.2%-12.9%) with similar patterns of associated factors and negative outcomes. Our findings demonstrated that ADHD is a prevalent mental disorder in Mozambique, and it is associated with similar comorbid profiles, predisposing factors, and negative outcomes as in other cultures.