Attention-deficit/hyperactivity disorder (ADHD) is defined by extreme levels of inattention–disorganization and/or hyperactivity–impulsivity. In DSM-IV, the diagnostic criteria required impairment in social, academic, or occupational functioning. With DSM-5 publication imminent in 2013, further evaluation of impairment in ADHD is timely. This article reviews the current state of knowledge on health-related impairments of ADHD, including smoking, drug abuse, accidental injury, sleep, obesity, hypertension, diabetes, and suicidal behavior. It concludes by suggesting the need for new avenues of research on mechanisms of association and the potential for ADHD to be an early warning sign for secondary prevention of some poor health outcomes. ► Health-related outcomes of ADHD are not well understood. ► ADHD is associated with elevated morbidity and mortality. ► ADHD is related to obesity but prospective data are lacking. ► ADHD is associated with elevated risk of accidental injury. ► Research on interventions targeting secondary health correlates of ADHD is necessary.