METHOD Participants The sample will consist of 50 child psychiatric patients with ADHD (20 ADHD-I, 20 ADHD-C and 10 ADHD-H) and 50 normal controls, aged 7-10. The inclusion criteria are patients who have clinically diagnosis of DSM-IV ADHD confirmed by the K-SADS-E, are aged 7-10, and have IQ > 80; and who and whose parents consent to this study. Participants will be excluded if they have a history of brain injury or epilepsy, visual/auditory deficit or were diagnosed as having motor disorder, obsessive-compulsive disorder, mental retardation, and depression. In order to recruit a population of pure ADHD (without other psychiatric comorbidities), children who are comorbid with oppositional defiant disorder (ODD) or conduct disorder (CD) were excluded, though the concurrence of ODD/CD and ADHD were high. Normal controls will be recruited from the local elementary school in the same geographical area.