Aim: The aim of this study was to evaluate the impact of pre- and perinatal factors on the risk of developing attention-deficit-hyperactivity disorder (ADHD). Method: We investigated the medical history of 237 children (206 male; 31 female) from Malmo, Sweden born between 1986 and 1996 and in whom a diagnosis of ADHD (Diagnostic and Statistical Manual of Mental Disorders-IIIR or IV) was subsequently made at the Department of Child and Adolescent Psychiatry, Lund University, and a reference group of 31 775 typically developing children from Malmo using data from the Swedish Medical Birth Register. Results: The results of multiple logistic regression analysis revealed that ADHD was significantly associated with a young maternal age (odds ratio [OR] for 5y increase 0.87; 95% confidence interval [CI] 0.76-0.99), maternal smoking (OR 1.35; 95% CI 1.14-1.60), maternal birthplace in Sweden (OR 2.04; 95% CI 1.45-2.94), and preterm birth less than 32 weeks (OR 3.05; 95% CI 1.39-6.71), and a male predominance (OR 6.38; 95% CI 4.37-9.32). Apgar scores at 5 minutes below 7 were significantly associated with ADHD in the univariable analysis (OR 2.60; 95% CI 1.15-5.90). The population-attributable fraction of ADHD caused by the perinatal factors studied was estimated to be 2.8%. Interpretation: The results indicate that the studied factors constitute weak risk factors for developing ADHD.