The severity of pulmonary hypoplasia in the patient we report was out of proportion to that of the diaphragm defect. Pulmonary hypoplasia is associated with abnormal diaphragmatic anatomy or function, and is known to occur as a secondary developmental defect in models of diaphragmatic dysfunction such as complete amuscularization [17] or phrenic nerve disruption [46]. It occurs in a surgical model of CDH in which a hernia is physically created in an in utero lamb [47,48]. However, the possibility that primary pulmonary developmental abnormalities occur with, rather than secondary to, diaphragmatic defects has been suggested by others based on a teratogenic model of CDH [49–51] and has long been suspected by clinicians who care for these patients. In addition, the high incidence of lobar abnormalities associated with CDH [52] supports the possibility that this disorder can be associated with a primary developmental pulmonary abnormality.