PURPOSE: To assess the change in configuration of the diaphragm between scans obtained at end inspiration and end expiration. MATERIALS AND METHODS: Two series of CT scans at end inspiration and at end expiration were obtained in 37 patients. We evaluated the changes in the type of anterior diaphragm, pseudotumor, undulation ofthe diaphragm, and diaphragmatic defect during the respiratory phases. RESULTS: The configuration of the anterior portion of the diaphragm changed between end inspiratory and end expiratory CT scans in 25(67.6%) of 37 patients. Diaphragmatic defect, diaphragmatic pseudotumor, and undulation of the diaphragm were more frequent at end inspiration (13.5%, 18.9%, 37.8%, respectively) than at end expiration (0%, 5.4%, 10.8%, respectively). CONCLUSION: There is a change in the configuration of the anterior portion of the diaphragm and we also observed differences in the visualization of diaphragmatic defects, pseudotumor, and undulation between scans obtained at end inspiration and end expiration.