The patient born with congenital diaphragmatic hernia (CDH) presents with a multitude of problems. The pulmonary hypoplasia associated with CDH results in an inadequate surface area for gas exchange, decreased cross sectional area of the pulmonary vascular tree, precocious muscularization of the pulmonary vessels, and probable surfactant deficiency. Elevated levels of circulating vasoactive mediators, as well as a heightened sensitivity to these mediators, further compounds the pulmonary hypertension associated with CDH. We have reviewed the pathophysiology of CDH, with specific reference to how this knowledge has affected clinical management.