During sleep changes in central and peripheral neurological pathways and muscle tone result in unique vulnerabilities in the respiratory system. Abnormalities of the respiratory system that are not apparent in wakefulness can become evident during particular sleep states, making overnight polysomnography (PSG) a valuable diagnostic indicator of the source as well as the severity of the abnormality. In this review these respiratory disorders are grouped according to whether they are attributable to upper airway collapse, poor gas diffusion or inadequate ventilation (respiratory effort). Inadequate ventilation may be secondary to abnormal respiratory drive (control) or to inadequate pulmonary muscle function. As a diagnostic tool, overnight PSG can help distinguish whether the origin of the disorder is central or peripheral on the basis of which sleep state is associated with greatest abnormality. The most common treatment interventions include supplemental oxygen, continuous positive airway pressure and non-invasive ventilation. Ventilation may be with either pressure or volume cycle devices. Overnight PSG is used for the titration and monitoring of these treatments since all these forms of respiratory support require regular adjustment to match patient requirements. The methods for titration and goals of optimal therapy in the paediatric sleep laboratory are discussed.