PURPOSE: The aim of this study is to evaluate the normal anatomy of the anterior diaphragm below the level of the xiphoid process by analyzing CT scans. MATERIALS AND METHODS: CT scans of 100 patients with no peridiaphragmatic lesions were retrospectively analyzed. All CT scans were performed with coverage of the whole diaphragm in the inspiration state. We evaluated the type of the anterior diaphragm, according to Gale's classification, the discontinuity of the anterior diaphragm (defect), the presence of a focal protrusion of the diaphragm (beak), and the thin line continuous with the diaphragm (line), and the relationship between the internal thoracic artery and the anterior diaphragm. Ed. Note: confirm wording. RESULTS: The frequency of defect, beak, and line were 17%, 27%, and 9%, respectively. Beak mainly (18/27) arose from the fusion between the anterior diaphragm and the transversus abdominis. The internal thoracic artery seen on CT was always located in the anterior portion of the transversus abdominis or transversus thoracis. CONCLUSION: The discontinuity of the anterior diaphragm and the focal protrusion of the diaphragm that mimics a hernia are relatively common variations of the anterior diaphragm. The internal thoracic artery may not be the cause of Morgagni foramen.