OF DEBATABLE INTEREST: Although the place of non-invasive ventilation (NIV) is indisputable in the management of acute respiratory failure during chronic obstructive pulmonary disease (COPD), where it significantly reduces the rate of intubation and complications and the number of days spent in intensive care, its interest is debated in the long term management of chronic obstructive respiratory failure (CORF). EFFICACY TO BE DEMONSTRATED: Although several short term studies confirm the efficacy of NIV on some physiological parameters and on the quality of sleep and quality of life in some patients, long term prospective studies are still too few and do not confirm these data on small series of patients and limited time. FOR CERTAIN CATEGORIES OF PATIENTS: It is legitimous to consider that sub-groups of patients respond to NIV, notably in cases of instable CORF non-controlled by medical treatments or by well-conducted kinesitherapy and oxygentherapy.