Abnormal growth and development of lymphatic pulmonary structures leads to severe hypoxia in congenital pulmonary lymphangiectasis (CPL). This case study aims to determine the cellular source and topographical distribution of the nitric oxide synthases in CPL. It studies the postmortem tissue of a term newborn with the clinical course and histological findings of CPL and three controls without pulmonary pathology. It was found that endothelial cells of pulmonary arteries and lymphatic structures stained significantly more for endothelial nitric oxide synthase protein in the CPL patient compared to the controls. The authors conclude that synthesis of endothelial nitric oxide synthase is upregulated in vascular and lymphatic endothelial cells in congenital pulmonary lymphanglectasis.