Attention-deficit/hyperactivity disorder (ADHD) is the most common behavioral disorder in childhood, with an estimated prevalence worldwide of 7%-17% among school-aged children. Modafinil is a centrally acting agent that is structurally and pharmacologically different from stimulants such as amphetamine and methylphenidate. It has been reported that modafinil is effective in diminishing the symptoms of ADHD. The aim of the present study was to further evaluate, under double-blind and placebo-controlled conditions, the efficacy of modafinil for ADHD in children and adolescents. Patients were 46 outpatients, children (35 boys and 11 girls) between the ages of 6 and 15 who clearly met the DSM-IV-TR diagnostic criteria for ADHD. All study subjects were randomly assigned to receive treatment with modafinil in a film-coated tablet, 200-300 mg/day, depending on weight (200 mg/day for <30 kg and 300 mg/day for >30 kg) (group 1) or placebo (group 2) for a 6-week double-blind, randomized clinical trial. The principal outcome measure was the Teacher and Parent ADHD Rating Scale-IV. Patients were assessed by a psychiatrist at baseline, 14, 28 and 42 days after the medication started. At 6 weeks, modafinil produced a significantly better outcome on the Parent and Teacher Rating Scale scores than placebo. Decreased appetite was observed more often in the modafinil group. The results of this study indicate that modafinil significantly improved symptoms of ADHD, was well tolerated, and may open a new window in the treatment of children with ADHD.