To help mimic some of the useful features of CT scans for early detection of diseases like lung cancer at a fraction of the cost, a knowledge‐assisted interactive 3D ribcage and lung reconstruction algorithm is proposed. The ribcage and lung reconstructions are both based on the typical PA (rear) and Lateral (side) X‐ray images that are already being acquired during preemptive screenings for lung cancer. Shared domain knowledge of human anatomy and solid modeling techniques are combined with knowledge automatically extracted from the X‐ray images through computer vision algorithms to transform a series of primitive template meshes into reconstructed ribs and lungs despite the fact that much of the 3D information is lost during the X‐ray process. An example of how the reconstructed lung geometry can be used to clip the portion of an approximate volume reconstruction to provide a supplementary interface to search for potential diseased areas is presented.