Nitric oxide (NO) is a cellular signaling molecule and a powerful vasodilator. NO modulates basal pulmonary vascular tone and it is important to reduce blood pressure and to treat hypoxemic respiratory failure, such as persistent pulmonary hypertension (PPHN) in newborns. PPHN is defined as a failure of normal pulmonary vascular adaptation at or soon after birth, resulting in a persisting high pulmonary vascular resistance. iNO therapy decreases the need of extracorporeal membrane oxygenation (ECMO) although it did not reduce mortality of these patients. Severe meconial aspiration syndrome is associated with PPHN, resulting in severe hypoxemia; iNO administration combined with HFV results in ameliorate oxygenation. The cause of hypoxemic respiratory failure in patients with congenital diaphragmatic hernia (CDH) is complex. CDH patients experienced oxygenation improvement after iNO therapy, but they can be often considered iNO poor responders. In some cases iNO therapy can reduce the need of ECMO in presurgical stabilization. The pathophysiology of respiratory failure and the potential risks differ substantially in preterm infants. Pulmonary hypertension can complicate respiratory failure in preterm babies. Current evidence does not support use of iNO in early routine, early rescue or layer rescue regimens in the care of preterm infants.