Abstract: Objective To report the method and the value of positron nuclide-¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) in radioguided surgery (RGS) in colorectal carcinoma.Methods Intravenously injected 111MBq ¹⁸F-FDG into 8 patients with colorectal carcinoma 2 hours before the operation. The detections were processed every hour and lasted five hours from the very beginning of the operations. We detected targets of tumors (T) and normal tissue (NT) by using a portable gamma-detecting probe. Additionally, we detected the proximal and distal edge of excised specimens, the tissue of colon wall 2cm to upper and lower edges of primary tumors of specimens, the lymph nodes of specimens. We were able to find the optimal time for posiron radioguidocl surgery (PRGS). Choosing the positive criterion T/NT ≥ 1.5, We were able to calculate the sensitivity of PRGS of the primary tumor, the specificity of colon wall tissue and excised edge, the sensitivity and specificity of lymph nodes.Results The optimal time for PRGS is the 5th~6th hour after intravenous injection of the ¹⁸F-FDG. The sensitivity of primary tumor detection is 100%. The specificity of colon wall tissue and excised edge is 71.9%. The sensitivity and specificity of lymph nodes detections are 83.3% and 68.9%.Conclusion PRGS had high sensitivity and specificity in judging the infiltrating range and lymph nodes metastasis in colorectal carcinoma.