Objective:To compare the imaging characteristics of 18F-fluorodeoxyglucose (FDG) PET/CT with same day diagnostic CT on breast cancer patients after surgery. Method:70 breast cancer patients after surgery were enrolled to take 18F-FDG PET/CT for 81 times. All patients underwent PET/CT for diagnostic purposes followed by diagnostic CT in the region of chest with breath hold. Results:31 PET/CT and 31 diagnostic CT results didn’t show any significant lesion. Another 50 studies displayed 372 lesions. The sensitivity,specificity,accuracy,positive productive value,and negative productive value of PET/CT were 88.0%,50.0%,84.9%,95.3%,26.8%,and those of diagnostic CT were 60.5%,31.6%,57.5%,88.6%,8.3%. As far as lymph node metastases were concerned,the sensitivity for PET/CT was 100%,but for diagnostic CT was 52.3%. As for bone and soft tissue metastases,the sensitivity for PET/CT was 98.1%,compared with 25.0% of diagnostic CT. As for pulmonary nodal metastasis,the sensitivity for PET/CT was 58.8%,but for diagnostic CT was 98.9%. Conclusion:PET/CT accurately detects more malignant lesions than CT does for lymph node and bone and soft tissue metastases. However,the diagnostic CT with breath hold will have an advantage over PET/CT on pulmonary metastases,especial small pulmonary node.