Abstract Objectives: The role of 18F-FDG (18F fluorodeoxyglucose) PET/CT** (Positron emission tomography) in the diagnosis, treatment and follow up of benign and malignant ovarian tumors had been investigated previously. The objective of the following study was to evaluate the predictive value of PET/CT in benign and malignant ovarian tumors and compare with computerized tomography and post-operative pathology. Materials and methods: In this retrospective study, a total of sixty nine cases with benign or malignant pelvic masses underwent laparotomy at our clinic. Postoperative pathology of the patients was recorded and PET/CT results were compared with ultrasonography, computerized tomography and postoperative pathology. Results: The ROCs and AUCs values four predictors were shown in Figure 1. The AUCs (95 % CI) values calculated for CA 125, ultrasonography (USG), PET/CT and CT were as follows: 0.855(0.752-0.958), 0.703(0.540-0.866), 0.681(0.514-0.848) and 0.631(0.463-0.799) respectively. CA 125 has the highest AUC value in order to predict the malignant potential of the patient. USG has the highest AUC value between the imaging techniques, following PET/CT and CT. Conclusion: According to this study, among four modalities that distinguish malignant potential preoperatively; CA125 is the best parameter. USG and PET provide similar benefits in detecting malignant ovarian masses preoperatively. Both of these parameters are superior to CT. Combination of CA125, USG and PET/CT may be useful in detecting malignant ovarian masses preoperatively, resulting in less invasive surgeries. ** 18F-FDG (18F fluorodeoxyglucose) PET/CT will be used as the PET/CT, later in this article.