Attention-deficit hyperactivity disorder (ADHD) is one of the most common chronic conditions of childhood, with adverse consequences that persist through adolescence into adulthood. Thus, the burden of illness associated with ADHD is high for affected individuals, their families, and society at large. This article reviews available information about ADHD-associated utilisation of healthcare resources, direct medical costs, and the costs or cost effectiveness of pharmacological interventions. Published estimates suggest that direct medical costs for youth with ADHD are approximately double those for youth without ADHD. Cross-sectional studies suggest that ADHD-associated incremental costs are highest for mental health services and pharmaceutical costs, and are greatest for youth with comorbid psychiatric conditions and for those being treated with stimulant medication. To guide relevant clinical and health policy, additional research is warranted on the following: source of increased costs observed among persons with ADHD; patient characteristics of those accruing high medical costs; and the long-term effect of ADHD treatment on direct and indirect costs.