Advances in the understanding of normal diaphragm embryogenesis have provided the necessary foundation for novel insights into the pathogenesis of congenital diaphragmatic hernia (CDH). Although diaphragm formation is still not completely understood, we have identified key structures and periods of development that are clearly abnormal in animal models of CDH. The pleuroperitoneal fold (PPF) is a transient structure which is the target for the neuromuscular component of the diaphragm. The PPF has been shown to be abnormal in multiple animal models of Bochdalek CDH; specifically, a malformation of the nonmuscular component of this tissue is thought to underlie the later defect in the complete diaphragm. Based on data from animal models and the examination of human postmortem tissue, we hypothesize that abnormal PPF development underlies Bochdalek CDH. Further, the understanding of the pathogenesis of rarer subtypes of CDH will be advanced by the study of various new animal models discussed in this review.