Abstract Background Colorectal cancer (CRC) is one of the most common malignancies worldwide and is a major health problem in developed countries with local and distant recurrences develops in 30–50% of patients during follow-up after primary surgery. Aim of Work The present study is aiming at emphasizing the role of PET/CT in Follow up of patients with colorectal carcinoma after treatment, as well as detection of local recurrence and distant metastasis. Methods The study included 25 patients with past history of colorectal cancer, they underwent PET/CT examination with the following protocol: Patients were fasting for at least 6 hrs before undergoing scanning. A standard dose of 1-1.5 mCi/kg of F-FDG was intravenously injected 45-60 mins before imaging then initially low dose CT was performed for attenuation correction. After that PET emission scanning was performed immediately after the CT. This was followed by diagnostic CT using IV contrast administration and hyperosmolar oral contrast (diluted mannitol solution) to achieve bowel distension. All data acquired a combined PET/CT in-line system. Results The study showed that there is significant paired differences between the number of local lesions as well as metastatic deposition detected in the initial and follow up PET/CT. Conclusion FDG PET/CT is extremely useful for therapy response assessment due to its capacity to help distinguish between residual metabolically active tumor and areas of necrosis and fibrosis, thus identifying which of these patients have achieved satisfactory functional remission and which one of them needs further treatment.