Congenital cystic adenomatoid malformation (CCAM), intralobar sequestration (ILS), extralobar sequestration (ELS), and lobar emphysema (LE) are well-accepted entities; however, certain findings are common to all, particularly the parenchymal maldevelopment characterizing CCAM. Isolated reports have described bronchial atresia (BA) in some specimens in all 4 entities, but this finding has not been evaluated in a prospective manner. With the aid of a dissecting microscope, we prospectively examined 47 lung specimens resected during the past 4 years and submitted with the clinical impression of ELS (n=11), ILS (n=11), CCAM (n=20), LE (n=4), and airway-esophageal communication (n=1). Most lesions were detected by prenatal ultrasound and were resected during infancy. The clinical impression and pathologic findings were compared. Pathologic examination revealed atresia of a lobar, segmental, or subsegmental bronchus in 100% of ELS, 82% of ILS, 70% of CCAM, and 50% of LE (those clinically recognized to have BA or minor CCAM) cases. Parenchymal maldevelopment that characterizes CCAM was present in 100% of CCAM cases (as expected by definition) as well as in 91% of ELS, 91% of ILS, and 50% of LE (those with BA) cases. Bronchial atresia is present in all ELS, most ILS and CCAM, and some LE cases, and its detection is greatly enhanced with the dissecting microscope. Bronchial atresia and CCAM nearly always coexist. It may be that both have the same etiopathogenesis with anatomic differences accounted for by aberrant genetic programs or other insults, perhaps modified by time of onset or duration.