Attention-deficit/hyperactivity disorder (ADHD) is a neurocognitive and behavior abnormality commonly seen in childhood and adolescence. Symptoms and consequences of ADHD and sleep problems frequently overlap, and their relationship is complex and bidirectional. To avoid inappropriate diagnosis and inadequate management, mental health professionals should assess sleep problems and disorders in children, adolescents, and adults with ADHD-related symptoms and in those with a diagnosis of ADHD. Screening for other psychiatric comorbidities and the side effects of medications, such as psychostimulants, is necessary when considering sleep complaints, because both have adverse effects on sleep.