Sleep is a vital process not only for survival but also to maintain physical and psychological health. ADHD is often associated with sleep difficulties. A reduction in sleep quality and duration can lead to significant behavioural and psychological manifestations. A comprehensive assessment should be carried out, involving a detailed sleep history, sleep diary, evaluation of any associated primary sleep disorders and an assessment of the role of ADHD medication. Management is ‘diagnostically driven’ and should include sleep hygiene with behaviour interventions, treating other comorbid conditions, optimising ADHD treatment and, if necessary, short-term use of sleep medication.