Mechanical ventilation is a life saving intervention in patients with respiratory failure. However, prolonged mechanical ventilation is associated with several complications. On the other hand, re-intubation following premature extubation is likely to increase patient morbidity and mortality. Therefore, it is imperative to terminate mechanical ventilation at the appropriate time and manner. "Weaning" is, by definition, the separation of the patient from the mechanical ventilator. For the better part of the intensive care patients, it can be uneventfully commenced once the primary ailment is appropriately managed. However, in cases involving acute respiratory failure on the basis of a chronic disease, such as acute exacerbation of a chronic obstructive pulmonary disease, weaning can prove challenging. Therefore, a number of studies have been conducted regarding the methods to be used for weaning. Noninvasive ventilation (NIV) describes ventilating a patient without utilizing an endotracheal airway, and is one of these methods. NIV can be used as an alternative treatment prior to intubation, a weaning model following intubation, and a treatment method or a failsafe measure following extubation. Recent studies indicate that in hemodynamically stable patients who have developed hypercapneic respiratory failure, NIV has proven to shorten weaning time and increase survival. Prophylactic use of NIV is promising in patients under risk for re-intubation. On the other hand, in non selected patients who have developed acute respiratory failure following extubation, it has been reported to be potentially harmful due to causing delay in re-intubation. As for the use of NIV in other clinical conditions and contradictory results, broad, multi centered and randomized clinical trials are needed. This article focuses on NIV throughout the weaning process.