Attention-deficit hyperactivity disorder (ADHD) is one of the most common childhood psychiatric conditions. In 2007, the Korean Academy of child and Adolescent Psychiatry developed Korean ADHD practice parameter. Advances in the scientific evidence of ADHD caused practice parameter to be modified and updated. The present guidelines developed by ADHD translational research center summarize current literature for the treatment of ADHD in children and adults. This parameter includes the clinical evaluation for ADHD, comorbid conditions associated with ADHD, clinical feature and course, research on the etiology of the disorder, and psychopharmacological and non-pharmacological treatments for ADHD.