Abstract: Positron emission tomography (PET) is a functional imaging modality that has been documented to be useful in patient care. The oncological PET imaging is utilized in a wide variety of neoplasms mainly for staging and follow-up, differentiation of equivocal morphological findings, therapy stratification and monitoring. As PET imaging is based on the physiological-mediated distribution of the administered tracer but not on anatomic information, the addition of CT imaging to PET may improve the interpretation of PET. The combined PET/CT offers several potential advantages over PET alone that may influence the clinical routine. PET/CT was introduced into clinical use only 3 years ago and has found widespread application within only 1–2 years. This article summarizes preliminary data of clinical applications for PET/CT in gastrointestinal tumors.