PURPOSE: To retrospectively evaluate the prevalent location and size of pulmonary embolism (PE) in anti-neoplastic chemotherapy patients by multidetector row CT (MDCT). MATERIALS AND METHODS: This study was conducted on 101 patients that were positively diagnosed with PE by CT. Among these patients, 23 had received or were undergoing chemotherapy. The location and the mean size of the largest PE were compared between anti-neoplastic chemotherapy patients and non-cancer patients using the Chisquare test and paired t-test, respectively. We also used a multiple linear regression to assess the risk posed by the other risk factors of PE. RESULTS: The most prevalent location of PE in patients on anti-neoplastic chemotherapy was in the lobar or segmental pulmonary arteries and was not significantly different from non-cancer patients. The size of the PE was smaller in patients on anti-neoplastic chemotherapy (1.14 mL [standard error = 0.29]) compared to non-cancer patients. (2.14 mL [standard error = 0.40]) (p < 0.05). CONCLUSION: The size of PE is smaller in anti-neoplastic chemotherapy patients than in non-cancer patients.