Nitric oxide (NO) is a diffusible gas with diverse roles in human physiology and disease. Significant progress in the understanding
of its biological effects has taken place in recent years. This has led to a better understanding of the pathobiology of pulmonary
hypertension (PH) and the development of new therapies. This article provides an overview of the NO physiology and its role
in the pathobiology of lung diseases, particularly PH. We also discuss current and emerging specific treatments that target NO
signaling pathways in PH.