Objective To evaluate the value of 18F-FDG PET/CT in diagnosis of renal cell carcinoma (RCC).Methods Totally 32 patients with RCC confirmed by pathology were analyzed retrospectively.The tumor diameter and maximum standard uptake values (SUVrmax) of different pathological types (clear and none clear RCC),different Fuhrman grades (high grade and low grade of clear RCC) and different clinical stages (distant and without distant metastases) were ana lyzed and compared.Results 32 RCC patients including 33 primary tumors,31 lesions were detected by PET/CT and 2 were false negative,the detection rate was 93.94％.The PET/CT findings of 31 primary lesions were mixed density soft tissue masses,and the 18F-FDG uptake accessible,above or below to the normal renal parenchyma;the other 2 lesions of PET/CT findings were normal.18F-FDG uptake of vein tumor thrombus in 8 cases and metastases in 19 cases were higher than the organs affected.The tumor diameter and SUVmax had no statistically significant difference in different pathological types and Fuhrman grades;The tumor diameter had no statistically significant difference,and SUVmax had statistically sig nificant (t=3.852,P=0.001) between different clinical stages.Conclusion The PET/CT findings of RCC primary lesion are varied,and small clear RCC with low Furhman grade may have no obvious abnormality and missed diagnosis;18F-FDG PET/CT has important value in the preoperative staging of RCC.