The costs associated with attention deficit hyperactivity disorder are considerable. These costs are incurred for the provision of health services, out-of-pocket family expenditures, educational services and juvenile justice services. In this review, we present the components of these costs and discuss factors likely to make a significant impact. It is shown that pharmaceuticals and ambulatory care services, in particular outpatient mental healthcare, account for the majority of healthcare costs. Finally, data are presented that suggest attention deficit hyperactivity disorder is associated with increased educational costs, while increased costs associated with juvenile justice may be due to mental health comorbidity. We speculate on future costs for attention deficit hyperactivity disorder given the introduction of new pharmaceutical agents and discuss projected increases in the prevalence of the disorder in under-represented populations.