Neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD), are commonly associated with sleep disturbances. The etiology of sleep disorders is multifactorial, such as congenital vulnerability of the quality and quantity of sleep, congenital abnormality of the sleep-wake pattern, comorbid sleep problems with developmental disorders, and sleep disturbances associated with pharmacological treatment.
 Obstructive sleep apnea disorder (OSAS) and restless legs syndrome (RLS) are closely associated with ADHD. OSAS in children not only presents with symptoms of sleep disturbances, but also with associated symptoms such as growth failure, neurocognitive and behavioral symptoms, ADHD-like symptoms, and enuresis. The first-line treatment is adenotonsillectomy. ADHD and RLS show high rates of comorbidity with common etiologies like iron deficiency and the alternation of dopamine transporter expression. Hypnotics are not effective for RLS, and a precise diagnosis is vital to treat RLS associated with ADHD.
 ASD is also associated with a high frequency of sleep disorders, especially insomnia, parasomnia, and sleep-wake disorders. The first strategy against sleep disturbances is behavioral intervention; however, pharmacological treatment is sometimes needed.
 In clinical practice, excessive daytime sleepiness was reported in children with ADHD or ASD, which might lead to a deficit in alertness. Alertness deficits associated with neurodevelopmental disorders remain uncertain, and so they should be assessed.
 The effect of stimulants on sleep in patients with ADHD differed among individuals, which might be the cause of insomnia and also treatment for ADHD and sleep hygiene. Non-stimulants are often effective for insomnia.
 Neurodevelopmental and sleep disorders are complex and bidirectional. Sleep disturbances should be taken into consideration in daily clinical practice.
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