Because of the common embryologic origin, alteration of the many factors modulating the development of the alimentary and the respiratory tract often results in structural abnormalities involving the two systems. Indeed, some of the most common embryologic disorders of the airways are frequently associated with anomalies of the gastrointestinal tract. Lung growth occurs as a series of tightly regulated events, depending on a number of factors, including developmental, genetic and environment ones. Abnormalities of any of these factors may causes developmental alterations of the lung leading to a group of disorders termed "bronchopulmonary-foregut malformations". These are usually sporadic, solitary cystic hamartomas, involving conducting airways, arteries, venous drainage, and lung parenchyma, which are now often discovered on routine prenatal sonography. While some lesions may be large and cause serious complications in the foetus or newborn, many will be asymptomatic at birth, raising controversy about management: simple observation or surgery and, if so, at what age? Over the past two decades molecular studies have started to shed light on the complex series of events that control proper formation of the lung, with the hope that a better understanding of the molecular basis of pulmonary maturation will allow the design of new therapeutic strategies.