PURPOSE: We attempted to determine the frequency of the type of anterior diaphragm and diaphragmatic abnormalities, and to ascertain whether these two may be correlated with respiration and patient's age. MATERIALS AND METHODS: Two hundred abdominal CT scans that were obtained at end expiration and 150 chest CT scans that were obtained at end inspiration were retrospectively reviewed for the evaluation of anterior diaphragmatic appearance, diaphragmatic defect, pseudotumor, and undulation. We evaluated the frequency of these findings and the differences of diaphragmatic appearance between the group above 60 years and the group under 59 years. RESULTS: The most common type of anterior diaphragm was lower(50.0%) on chest CT scans and superior (32.5%) on abdominal CT scans;thus, a significant relationship with respiration was observed. Diaphragmatic defect, pseudotumor, and undulation were found in 15.1%, 16.0%, 22.6% of all 350 patients, respectively. Diaphragmatic defect did not change significantly with the respiration or the type of anterior diaphragm. Pseudotumor and undulation, which were more common on chest CT scans and the lower type of anterior diaphragm, demonstrated a trend to change with respiration. Diaphragmatic defect, pseudotumor, and undulation were more common in older age above 60 years(26.4%, 23.6%, 36.8%, respectively) than in under 59 years(7.3%, 10.7%, 12.6%, respectively). CONCLUSION: Anterior diaphragmatic appearances may not be constant but may change with respiration. Respiration and aging process may be the main causes of diaphragmatic abnormalities.