The term alveolar capillary dysplasia refers to complex vascular abnormalities which have recently been identified in some infants with persistent pulmonary hypertension. We report four cases admitted to our institution for severe pulmonary hypertension unresponsive to maximal cardiorespiratory support, including high-frequency ventilation, inhaled nitric oxide and extracorporeal membrane oxygenation. The four infants died of refractory hypoxaemia. The diagnosis of alveolar capillary dysplasia was established by necropsy. We have used these cases as an opportunity for a thorough review of the literature containing comments regarding aetiology, pathophysiology, clinical presentation, associated malformations and treatment trials. CONCLUSION: alveolar capillary dysplasia should be ruled out in all newborn infants presenting severe idiopathic pulmonary hypertension associated with malformations. Open lung biopsy may prevent from using costly, invasive and probably ineffective procedures such as extracorporeal membrane oxygenation.