It is called ADHD in China and is one of the most common behavioral disorders of childhood. It is characterized by inattention and short attention span, hyperactivity and impulsivity that are incompatible with age and developmental level, often accompanied by learning difficulties, conduct disorder, mood disorder and oppositional defiance disorder. The prevalence rate is 3% to 7%, with a male to female ratio of 4 to 9:1. There are many possible causes such as genetic factors, environmental factors, neuroanatomical and neurochemical factors, and central nervous system damage.