In many ICU's in these days non-invasive mask ventilation is a technique in addition to the traditional invasive ventilation via endotracheal tube if the patient is able to cooperate. If contraindication (mucus retention, swallowing disorders, acute neurologic disorders, circulatory instability) and definition of interruption criteria are regarded, the method is safe. Besides its use for exacerbation of chronic obstructive pulmonary disease, especially the cardiogenic, pulmonary oedema is an indication which is supported by several studies. Other conditions such as pneumonia and ARDS have only been observed in relatively small studies. According to pathophysiologic pathways the use of non-invasive techniques seems limited to not-so-advanced stages of the disease in these cases. Considering the growing importance of this technique for the weaning procedure after long-term mechanical ventilation should be established at every ICU.