he pulmonary circulation is comprised of the pulmonary vascular tree (arteries, capillaries, veins), the pulmonary parenchyma, and the process during which deoxygenated blood traverses the pulmonary vascular tree to become oxygenated before returning to the left heart. In contrast to the systemic circulation, the pulmonary circulation exists at a pressure one-sixth that of the systemic circulation. A variety of forms of congenital heart disease (CHD) include abnormalities of the pulmonary circulation, some of which may result in serious symptoms. Mathematical modeling has been increasingly used to characterize the pulmonary circulation and improve our understanding of pulmonary hemodynamics in acquired and congenital heart disease. This chapter presents the state-of-the-art considerations of and methods for modeling the pulmonary circulation. A brief introduction of the pulmonary circulation’s physiology is followed by a clinical overview of CHD-related pulmonary vascular abnormalities, a summary of current mathematical modeling techniques, and example of real-world application of these techniques.