Purpose: A rising CEA level after the resection of colorectal cancer is an early indicator of tumour recurrence. However, conventional imaging techniques have limited sensitivity for detecting recurrent disease in such patients. Our group has evaluated the role of Positron Emission Tomography with 18F-Fluorodeoxiglucose (FDG-PET) in this clinical situation.Material and Methods: Seventy-two patients with abnormal CEA levels and normal results of conventional methods of tumour detection were studied with FDG-PET. The PET results were compared with pathologic findings (n = 25) long-term radiological (n = 9) and clinical follow-up (n = 38). Influence of PET findings in therapeutic management was also considered in this study.Results: PET detected lesions in 63/72 patients (87.1%). Metabolic imaging showed metastases in the liver (44.1%), ganglionar nodes (27.5%), local recurrence (20.4%) and lung metastases (8%). Overall, the sensitivity of PET was 94.4%, specificity was 83.3%, the positive-predictive value was 97.1%, the negative-predictive value was 71.4% and the diagnostic accuracy was 92.8%. FDG-PET findings change therapeutic decision in 68/72 patients (94.1%)Conclusion: When conventional examinations are normal, FDG-PET is a valuable imaging tool in patients who have rising CEA level after colorectal surgery. Metabolic imaging represents a very cost-effectiveness diagnostic procedure in this clinical situation, avoiding unnecessary invasive techniques.