Attention deficit/hyperactivity disorder (ADHD) is a frequent disorder that often persists in adulthood. Persistent ADHD is known to be a serious risk factor for other disorders in adulthood, and adults with ADHD often report on sleep disorders. Despite this, only few studies have investigated the subjective and objective quality of sleep in adults suffering from ADHD. Previous studies have revealed seriously impaired subjective sleep quality and increased nocturnal motor activity in spite of essentially normal standard polysomnographic parameters in this patient group. However, primary sleep disorders such as sleep apnea syndrome or restless legs syndrome (RLS) may be misdiagnosed as ADHD. Moreover, ADHD and primary sleep disorders may occur as comorbidities. In particular, RLS was suggested to be highly associated with ADHD, indicating a probable common central nervous dopaminergic dysfunction. To date, larger studies with adequate sample sizes that compare sleep in adult patients with ADHD, healthy control groups and patients with other primary sleep disorders are still lacking.