Neurodevelopmental disorders (NDDs) are often characterised by sleep problems, and recent evidence indicates alterations of the sleep electroencephalographic (EEG) oscillations in these patients. Sleep microstructure plays a crucial role in cognitive functioning and brain maturation. In this view, modifications in sleep EEG oscillations in NDDs could further impair the cognitive maturation process in these patients. We provide an overview of sleep microstructure alterations observed in three NDDs without intellectual disabilities (attention-deficit/hyperactivity disorder, high-functioning autism/Asperger syndrome and developmental dyslexia) and their relationships with the disorders' phenomenology. For each NDD, we discuss empirical evidence of altered EEG oscillations, and we consider their interaction with patients' cognitive and behavioural functioning, with the aim to elucidate their functional meaning. We highlight the limits of the present literature and propose possible future directions while underlining the clinical relevance of the research in this field. Beyond confirming the importance of sleep management in atypically developing children, the review findings suggest that sleep EEG oscillations in NDDs could become a target for specific clinical intervention.