A 65-year-old man underwent computed tomography (CT) of the abdomen during evaluation for anemia which showed a 10 cm right renal mass and inferior vena cava (IVC) thrombus. Positron emission tomography (PET)/CT revealed uptake of flurorodeoxyglucose (FDG) within only the tumor mass and thrombus. Right radical nephrectomy and IVC thrombectomy with IVC patch graft reconstruction were performed. Final pathology showed pT3bNxMx renal cell carcinoma (RCC) with IVC thrombus composed of poorly differentiated RCC. There is no evidence of recurrence at one year follow-up. We discuss the role of PET in RCC.