Chronic hypoxia compromises the development of both airways and pulmonary vasculature following exposure before or after birth. It also impairs adaptation to extrauterine life. The immediate morbidity and mortality is high, and long-term sequelae in terms of lung structure, and thus function, are common, particularly in premature infants. Chronic lung disease or bronchopulmonary dysplasia can develop with or without cor pulmonale. The extensive fibrotic disease of classical bronchopulmonary dysplasia has become uncommon with the development of improved treatment strategies, but the development of the lung periphery can still be compromised as more immature babies survive. This article highlights the landmarks of normal lung development together with the principal established and newly recognized features of exposure to chronic hypoxic in the young. In doing so, it indicates promising areas for research activity.