Non invasive ventilation encompasses all techniques of ventilatory support which do not require an endotracheal approach. Interfaces are available for coping with most situations, with an acceptable control of leaks, of patient comfort, even in severely ventilator dependant subjects. A wide variety of home ventilators, also used in hospital wards outside of intensive care units, are available, either volume-cycled, pressure-cycled, or "multi-mode", allowing flexibility in prescription and adjustment of treatment. Pressure assisted ventilation with PEEP (bi-level positive airway pressure) has become in most centres the "default approach". A thorough understanding of modes and settings is required for optimal adjustment of NIV, patient comfort and treatment efficacy.