Beijing Willingjet Science Co., Ltd.

Primary Objective: To demonstrate the superiority of individually titrated doses of MPH HCl extended-release capsules (Medikinet® retard) over placebo in the treatment of Chinese children and adolescents (6 to <18 years old) with ADHD based on the change from baseline in the ADHD-IV Parent Rating Scale total score after 4 weeks of stable dose treatment. Secondary Objectives: To investigate the safety of Medikinet® retard versus placebo in the treatment of Chinese children and adolescents with ADHD. To investigate the PK of MPH HCl in Chinese children and adolescents after administration of 10 mg, 20 mg, or 30 mg Medikinet® retard.