We assessed the maturity of the lungs and the radial count in 10 infants with congenital diaphragmatic hernia who died in the immediate perinatal period. The lungs were all immature, with a histologic appearance of less than stated gestational age. The ipsilateral lungs were less mature in appearance than were the contralateral ones. The radial count, an assessment of acinar complexity, was reduced in all cases, and once again the ipsilateral lung was more affected. We present evidence that, in 4 of 6 lungs, volumes were more reduced than predicted from the radial count, and this may be due to loss of (airway) units. We have discussed the controversy about the appearance of the acinus in diaphragmatic hernia and present reasons to explain this. Hyaline membrane disease often occurs in diaphragmatic hernia, even at full term. Intra-alveolar hemorrhage is a common complication of diaphragmatic hernia.