Objective To analyze the clinical value of 18F-deoxyglucose (18F-FDG) positron emission computed tomography (PET/CT) in postoperative recurrence and metastasis of colorectal cancer. Methods A total of 80 patients with colorectal cancer treated by operation in the hospital were examined with 18F-FDG PET/CT and enhanced CT. The diagnostic accuracy, sensitivity and specificity of 18F-FDG PET/CT and enhanced CT examination for postoperative recurrence and metastasis were compared with the results of biopsy and pathology or reoperation as the golden standard. Results There was no significant difference in specificity between 18F-FDG PET/CT and enhanced CT scan for postoperative recurrence (χ2 =2.036, P>0.05). The accuracy (χ2 =5.766, P<0.05) and sensitivity (χ2 =4.547, P<0.05) of 18F-FDG PET/CT were significantly higher than those of enhanced CT scan. The specificity (χ2 =6.176, P<0.05), accuracy (χ2 =13.491, P<0.05) and sensitivity (χ2 =7.372, P<0.05) of 18F-FDG PET/CT for postoperative metastasis were significantly higher than those of enhanced CT scan. Conclusion Compared with the traditional enhanced CT scan, the accuracy and sensitivity of 18F-FDG PET/CT are higher in the diagnosis of postoperative recurrence of colorectal cancer, and the accuracy, specificity and sensitivity are higher for postoperative metastasis.