Molecular imaging, such as positron emission tomography (PET) has been widely used in clinical oncology. Currently, F18-labeled fluorodeoxyglucose (18F-FDG) PET/CT accounts for the majority of all molecular imaging procedures. Accurate and reliable imaging studies are needed to properly stage cancer patients for treatment plans and to provide imaging parameters and biomarkers for optimal assessment of therapeutic response. Immunotherapy and targeted therapies have become the standard of practice for some oncology treatments. Molecular imaging, such as PET, is now playing a greater role in treatment selection and monitoring treatment response. The success of FDG PET is also recognized with certain limitations. Special attention has been devoted to the development of new tracers for better evaluation of tumor burden and immunotherapy response. In this chapter, we will outline the clinical utility of FDG PET (PET/CT) and provide a brief discussion of new radiotracers for renal cell carcinoma (RCC).