Noninvasive ventilation (NIV) has assumed a prominent role in the treatment of patients with both hypoxemic and hypercapnic acute respiratory failure (ARF). The main theoretic advantages of NIV include avoiding side effects and complications associated with endotracheal intubation, improving patient comfort, and preserving airway defense mechanisms. Factors that affect the success of NIV in patients with ARF are clinicians' expertise, selection of patient, choice of interface, selection of ventilator setting, proper monitoring, and patient motivation. Advances in the understanding of the physiologic aspects of using NIV through different interfaces and ventilator modalities have improved patient-machine interaction, thus enhancing favorable NIV outcome.