During noninvasive ventilation (NIV) for acute respiratory failure, the patient's comfort may be less important than the efficacy of the treatment. However, mask fit and care are needed to prevent skin damage and air leaks that can dramatically reduce patient tolerance and the efficacy of NIV. Choice of interface is a major determinant of NIV success or failure. The number and types of NIV interface has increased and new types are in development. Oronasal mask is the most commonly used interface in acute respiratory failure, followed by nasal mask, helmet, and mouthpiece. There is no perfect NIV interface, and interface choice requires careful evaluation of the patient's characteristics, ventilation modes, and type of acute respiratory failure. Every effort should be made to minimize air leaks, maximize patient comfort, and optimize patient-ventilator interaction. Technological issues to consider when choosing the NIV interface include dead space (dynamic, apparatus, and physiologic), the site and type of exhalation port, and the functioning of the ventilator algorithm with different masks. Heating and humidification may be needed to prevent adverse effects from cool dry gas. Heated humidifier provides better CO(2) clearance and lower work of breathing than does heat-and-moisture exchanger, because heated humidifier adds less dead space.