Abstract: Objective To assess the value of ¹⁸F-FDG PET/CT for the diagnosis of fever of unknown origin(FUO). Methods The clinical data about FUO patients who underwent ¹⁸F-FDG PET/CT in Department of Fever-Related Diseases, Chinese PLA General Hospital, from January 2012 to December 2012, were retrospectively analyzed. Their ¹⁸F-FDG PET/CT diagnosis and final clinical diagnosis were compared. Results Of the 78 FUO patients included in this study, 21(26.9%) were diagnosed with infectious diseases, 9(11.5%) were diagnosed with connective tissue diseases, 24(30.8%) were diagnosed with malignant tumor, 9(11.5%) were diagnosed with miscellaneous diseases, and 15(19.3%) were not clearly diagnosed. The accuracy, sensitivity, specificity, positive and negative predicting value of ¹⁸F-FDG PET/CT were 75.6%, 100%, 44.1%, 69.8% and 100%, respectively, for the diagnosis of FUO. Conclusion The sensitivity and negative predicting value of ¹⁸F-FDG PET/CT are very high for the diagnosis of FUO and should thus be popularized in the diagnosis of malignant tumors.