OBJECTIVES: Attention-deficit hyperactivity disorder (ADHD) is a common disorder that is associated with broad functional impairment among both children and adults. The purpose of this project was to review literature on the economic costs of ADHD, as well as potential economic benefits of treating this condition. METHODS: A literature search was performed using MEDLINE to identify all published articles on the economic implications of ADHD, and authors were contacted to locate conference abstracts and articles in press that were not yet indexed. In total, 22 relevant items were located including published original studies, economic review articles, conference presentations, and reports available on the Internet. RESULTS: Results of medical cost studies consistently indicated that children with ADHD had higher annual medical costs than either matched controls (difference ranged from $503 to $1343) or non-matched controls (difference ranged from $207 to $1560) without ADHD. Two studies of adult samples found similar results. A limited number of studies have examined other economic implications of ADHD including costs to families; costs of criminality among individuals with ADHD; costs related to common psychiatric and medical comorbidities of ADHD; and costs of accidents among individuals with ADHD. Treatment cost-effectiveness studies have primarily focused on methylphenidate, which is a cost-effective treatment option with cost-effectiveness ratios ranging from $15,509 to $27,766 per quality-adjusted life year (QALY) gained. CONCLUSIONS: A growing body of literature, primarily published in the United States, has demonstrated that ADHD places a substantial economic burden on patients, families, and third-party payers. Recognition, diagnosis and treatment of ADHD are increasing in Europe and Australia, and future studies may document the economic burden of ADHD in these areas. As new treatments are introduced, it will be important to evaluate their cost-effectiveness to provide an indication of their potential value.