We investigated the effect on daytime respiratory function and quality of sleep, of providing adequate ventilation either by intermittent positive pressure ventilation (IPPV) or by continuous positive airways pressure (CPAP) both administered through a nose mask in a group of seven patients with severe thoracic kyphoscoliosis. All night control sleep studies were performed with and without ventilatory assistance. Patients underwent standard polysomnography including all night measurements of transcutaneous CO2 (tcCO2) and arterial oxyhemoglobin saturation (SaO2). Awake arterial blood gas tensions (ABGs), respiratory muscle strength (Pmus), and lung function tests were measured in the sitting position. Follow-up studies after three months of treatment showed normal sleep patterns, improvement in daytime ABGs, lung volumes, and respiratory muscle strength. We concluded that maintenance of nocturnal ventilation by either nasal CPAP or nasal IPPV in patients with nocturnal respiratory failure does significantly improve clinical measurements of respiratory function and quality of sleep.