The acute respiratory distress syndrome (ARDS) is characterized by a maldistribution of pulmonary blood flow towards non-ventilated atelectatic lung areas being the main reason for intrapulmonary right-to-left shunt with the consequence of severe arterial hypoxemia. The application of inhaled nitric oxide (iNO) is a therapeutic option to selectively influence pulmonary blood flow in order to improve arterial oxygenation and to decrease pulmonary artery pressure without relevant systemic side effects. Although randomized controlled trials demonstrated no survival benefit in patient populations covering the entire severity range of acute lung injury, iNO represents a feasible rescue treatment for ARDS patients with severe refractory hypoxemia and is, therefore, an important option for ARDS therapy in specialized centers.