Noninvasive ventilation (NIV) is a standard of care for the treatment of exacerbation of chronic obstructive pulmonary disease, to prevent intubation and reduce morbidity and mortality. The need for humidification of NIV gas is controversial. Some unique aspects of NIV conspire to alter the delivered humidity and airway function. In the presence of air leaks, unidirectional air flow dries the airways and increases airway resistance. Patient comfort is also a critical issue, as tolerance of NIV is often tied to patient comfort. This paper provides the arguments for and against routine humidification during NIV in the hospital setting. Data from clinical research demonstrate the effects of delivered humidification on relevant physiologic variables. The impact of humidification on NIV success/failure remains speculative.