Subjects and Methods: Participants will consist of 20 children with ADHD-C, 20 with ADHD-I, 10 with ADHD-H and 50 controls without ADHD in the age range of 7 to 10. The measures include the psychiatric interviews (Chinese K-SADS-E), neuropsychological tests (WISC-III, Cancellation Test, Digit Span, Trail Making Test, CPT, Circle Tracing Test), self-administered rating scale (SNAP-IV), and investigator administered assessment (CGI and Behavior Observation Ratings).