respectively. The overall sensitivity, specificity and accuracy of 18 F-FDG PET/CT in detection of metastatic lymph node was 85.8%, 89.8%, and 89%, respectively. PET/CT shows low sensitivity (77.3%) and specificity (25%) in analyzing mesorectal fascia involvement. The overall sensitivity of 18 F-FDG PET/CT in M staging was 100%. Conclusions: 18 F-FDG PET/CT is highly sensitive for initial T staging of rectal cancer especially in advanced disease. This imaging modality is highly accurate in detection of metastatic lymph nodes and liver metastases, but it has no role in defining of mesorectal fascia involvement. Therefore, 18 F-FDG PET/CT should be incorporated routinely in preoperative staging together with conventional imaging.