Several investigators have reported an increased frequency of attention/hyperactivity symptoms in international adoptees, though population-based studies are lacking. In this national cohort study, we aimed to determine the prevalence of ADHD medication in international adoptees in Sweden, in comparison to the general population. A further purpose was to study gender, age at adoption and region of origin as predictors of ADHD medication in international adoptees. The study population consisted of all Swedish residents born in 1985–2000 with Swedish-born parents, divided into 16,134 adoptees, and a comparison population of 1,326,090. ADHD medications were identified in the Swedish Prescribed Drug Register during 2006. Logistic regression was used to calculate the odds ratios. The rates of ADHD medication were higher in international adoptees than in the comparison population for both boys (5.3 vs. 1.5% for 10–15-year olds) and girls (2.1 vs. 0.3% for 10–15-year olds). International adoptees from all regions of birth more often consumed ADHD medication compared with the majority population, but the age and sex adjusted odds ratios were particularly high for adoptees from Eastern Europe, Middle East/Africa and Latin America. Adjusting for maternal education and single parenthood increased the odds ratios even further. The risk also increased with higher age at adoption. Adoptees from Eastern Europe have a very high risk for ADHD medication. A structured identification and support programme should be tailored for this group. Adoptees from other regions have a more moderately increased risk, which should be communicated to adoptive parents and to professionals who care for adoptees in their clinical practice.