Background. No bibliographical references exist in non-invasive nasal mask ventilation because of acute pneumonia in McCune-Albright syndrome till now. Case report. Emergency hospitalisation of a 16-year-old boy due to an acute pneumonia with acute respiratory failure (pH 7,27, pCO₂ 8,96 kPa, SpO₂ 92% despite 6 l/min O₂-supplement). History: McCune-Albright syndrome already in the 3rd life month diagnosed. In the course of a disease multiple bone fractures of all extremities. During the last years recurrent respiratory infections. Since some month frontal headache in the morning. X-ray-thorax: pneumonia of the left lower lobe. Sputum-microbiology: Streptococcus pneumoniae. Spirometry: most severe restrictive ventilatory disorder also after pneumonia went down (inspiratory vital capacity 200 ml, about 10% of rated value). Pulsoximetry: recurrent short O ₂-desaturation in the morning till 60% despite 3 IO ₂-supplementation. Course and therapy: well tolerated non-invasive nasal mask ventilation in controlled mode with stop of the frontal headache. Initial ventilation with a duration of 24 h/d, later only at night and at afternoon nap with 0,5 l O₂/min. During mask ventilation, antibiotical therapy and physiotherapy normalisation of the blood gas value, O₂-saturation (measured by pulsoximetry), inflammatory parameters and slightly risen inspiratory vital capacity up to 370 ml. Discussion. In patients with acute respiratory failure due to restrictive ventilatory disorder because of weakness of "breath-pump" the possibility of non-invasive mask ventilation should be considered, to avoid Intubation on intensive care units and tracheotomy.