The availability of algorithms to create three-dimensional (3D) models from medical images has made it possible to render and build patient-specific reconstructions of individual body parts. In the present study, this technology was used to create 3D models of pediatric hearts for use in medical device development. Digital models were created using CT datasets of pediatric hearts and commercially available 3D image processing software. Using this software, stacked CT data were viewed, and pixels representing the heart and rib cage were selected and rendered as 3D models. Stereolithography and 3D printing technology were used to create rigid and flexible physical heart models (biomodels) from the digital models. Twelve on-screen models of the thorax and cardiac structures were created from cardiac CT scans obtained from 11 patients with and without congenital heart disease (median age, 3 years; range, 2 days to 13 years). Rigid and flexible physical heart models were generated from the digital models to provide tactile and visual information. 3D models of pediatric cardiac and chest anatomy provide enhanced understanding and tactile representation of complex anatomy. Precise representation of the spatial relationships between anatomic structures is particularly useful during the development and placement of medical devices.