Bronchopulmonary dysplasia (BPD) is a chronic respiratory disease that develops as a consequence of perinatal/neonatal lung injury, and it is one of the most important sequelae of premature birth. In this article we discuss recent changes in the definition of BPD, the main differences between the old and the new form and we summarize recent data on long-term respiratory outcome. The diagnosis of BPD is currently based on the need for supplemental oxygen for at least 28 days after birth, and its severity is graded according to the respiratory support required at 36 postmenstrual weeks. The "new BPD" is mainly a developmental disorder in which the immature lung fails to reach its full structural complexity. Longitudinal studies on children with BPD identified, at all ages, a greater need to use inhaled asthma medication and a significant airflow obstruction. Whether survivors of BPD and prematurity have a risk of developing a COPD-like phenotype with aging is a question that only lung function studies extended to middle-age and beyond will answer.