Attention deficit hyperactivity disorder (ADHD) is the most common behavior disorder, with the prevalence of 3% to 6% in children and adolescents. The patients' academic achievements, professions and social livings are impaired. Comorbid antisocial behavior, substance abuse and delinquency burden family and society. Stimulants used to be the first line drug. But the medication compliance is poor because of strict drug administration. Atomoxetine is a new non-stimulant drug, which can effectively improve ADHD symptoms. But it achieves effect slowly, the drug responses differ significantly, and side effects interfere compliance. Since genetic factors is the most important cause for different drug responses, this project studies candidate genes potentially associated with atomoxetine medication, with the aim to find 2 to 3 gene polymorphisms influencing the drug response of ADHD. The study adopts cohort design. A sample of more than 100 ADHD cases with atomoxetine medication is to be collected. The rapid genotyping of large sample depends on high-through laboratory. New statistic method is to be used to improve the sensitivity of the target gene detection. There has been no such report in country and overseas. This project will provide basic information for forecasting drug response, improving clinical effects, tolerance and long-term compliance.

Inclusion Criteria:

• The subject should meet with the DSM-IV ADHD criteria, confirmed by semi-structured interview.
• The subject has not accepted any treatment for ADHD before, or he/she received methylphenidate or atomoxetine treatment but has stopped for 1 or 4 weeks respectively.
• Han Chinese
• Parent sign the informed consent

Exclusion Criteria:

• Who are allergy to atomoxetine
• Who can not complete the titration procedure because of untolerable of the side effect
• Who combined other psychotropic drugs or non-drug intervention for ADHD.
• Children who can not be compliant with the blood withdraw.