This study was designed to investigate the factors affecting linear distortion in orthopantomography. A test model was constructed with metallic rods positioned to simulate maxillary teeth from the first permanent molar to the lateral incisor. In addition to examining the effects of varying the tilts of the test rods in a mesio-distal or bucco-palatal direction, spatial position changes (sagittal displacement, transverse displacement and horizontal rotation) of the test model were evaluated by determining the magnification changes in the width and length of the test rods. Results showed that significant errors occurred with all variations in magnification when test rods were inclined buccopalatally (