Pulmonary vein stenosis of ex-premature infants is a complex problem with poor survival, delayed diagnosis, and unsatisfactory treatment. The lack of concordance in twins suggests epigenetic or environmental factors may play a role in the development of pulmonary vein stenosis. In ex-premature infants with pulmonary hypertension and bronchopulmonary dysplasia a focused echocardiographic assessment of the pulmonary veins is required with further imaging if the echocardiogram is inconclusive.