Background. Attention-deficit hyperactivity disorder (ADHD) is one of the most common psychiatric disorders among children. The aim of this study was to evaluate risk factors for ADHD in children. Method. In this case-control study, 404 children between 4 and 11 years old were selected by cluster sampling method from preschool children (208 patients as cases and 196 controls). All the participants were interviewed by a child and adolescent psychiatrist to survey risk factors of ADHD. Results. Among cases, 59.3% of children were boys and 38.4% were girls, which is different to that in control group with 40.7% boys and 61.6% girls. The chi-square showed statistically significance (P value < 0.0001). The other significant factors by chi-square were fathers' somatic or psychiatric disease (P value < 0.0001), history of trauma and accident during pregnancy (P value = 0.039), abortion proceeds (P value < 0.0001), unintended pregnancy (P value < 0.0001), and history of head trauma (P value < 0.0001). Conclusions. Findings of our study suggest that maternal and paternal adverse events were associated with ADHD symptoms, but breast feeding is a protective factor.