Objective:To evaluate the diagnostic value of 18F-FDG PET/CT whole body imaging in detecting of focal high uptake in the junctional zone of proctosigmoid. Methods:18F-FDG PET/CT whole body imaging was performed in 2241 patients, 193 patients with abnormal focal uptake in the junctional zone of proctosigmoid were retrospectively reviewed and followed up. These abnormalities were compared with the final diagnosis obtained from pathological conformation, other imaging modalities diagnosis and clinical follow-up information. Results:There were 101 physical uptake in 193 abnormalities,38 were verified malignant tumors, 54 were benign lesions, in which there were 9 with inflammation. There were significant differences in SUVmax (both early imaging and delay imaging) between physical uptake and lesion uptake;and in delay SUVmax between malignant and benign lesions. There were no differences in early SUVmax between malignant and benign lesions.Conclusion:18F-FDG PET/CT has important role in detecting abnormal uptake in proctosigmoid tumor, in identifying the malignant and benign lesions by double-phase imagings.