The use of inhaled nitric oxide (iNO) in newborn hypoxemic respiratory failure is based on the evidence of selective pulmonary vasodilation, without systemic side effects. It is use in more than 34 weeks old newborns, with severe acute pulmonary hypertension and right-left extrapulmonary shunt. In the other cases (i.e. pneumonia, sepsis, ARDS), the therapeutic effect is less evident; no final data are available on the use of iNO in pre-term babies. The recommended dosage is 20 ppm, scaling down until 5 ppm and the 40 ppm should never be reached. The length of treatment is variable, usually no more than 7 days and the weaning should be progressive. In conclusion,the use of iNO in newborns with persistent pulmonary hypertension reduces the need of ECMO, but does not substantially modify the outcome.