The testing procedure is as follows: (1) In addition to clinical diagnosis, subjects' mothers will receive K-SADS-E interview to make psychiatric diagnosis. (2) All subjects (ADHD group and normal controls) will be assessed IQ and a series of time perception tasks. Their parents will complete the SNAP-IV and CPRS-R:S and teachers will complete the CTRS-R:S. (3) After receiving medication for ADHD for 3 months and for one year, children will be reassessed by time perception tasks and CPT. Their parents and teachers will be asked to complete the same rating scales.