PURPOSE: Attention deficit hyperactivity disorder (ADHD) is a syndrome characterized by inattention, impulsive disruptive behavior, impaired concentration, and motor restlessness. This study examined the relationships among electroencephalographic (EEG) findings, stimulant use, and seizure occurrence in children with ADHD. METHODS: We retrospectively studied 308 children with ADHD who visited the neuropsychiatric clinic of our hospital from January 2001 to December 2005. We retrospectively analyzed age distribution, etiology, abnormal EEG findings, and use of CNS stimulants. Among these children, brain waves was recorded in 84 patients. RESULTS: Eighty-four children (72 males, 85.7%, 9.3 years mean age; 12 females, 14.3%, 8.0 years mean age) with ADHD had electroencephalograms (EEGs) performed at our institute. Nineteen patients (22.6%) demonstrated epileptiform abnormalities, and 65 (77.4%) demonstrated normal EEGs. Stimulant therapy was applied to 59 of 84 patients (70.2%). Seizures occurred in 1 of 65 patients with a normal EEG (incidence, 1.5%) and 3 of 19 treated patients with epileptiform EEGs (incidence, 15.7%). CONCLUSION: These data suggest that patients with normal EEGs have minor risk for seizure. In contrast, patients with epileptiform EEGs have higher risk for seizure than patients with normal EEGs.