Abstract: Metastatic renal cell carcinoma (mRCC) is insensitive to both radiotherapy and chemotherapy; hence, the prognosis of patients with mRCC is poor. With the development of molecular targeted therapy, various targeted drugs, such as sunitinib and sorafenib, have greatly improved the prognosis of mRCC. However, targeted therapy is not effective for some patients, and targeted drugs may also cause related adverse reactions. Therefore, early non-invasive assessment of tumor response to targeted drugs is particularly important to allow patients and physicians to decide on the best course of treatment. However, researchers worldwide have not yet found an ideal biomarker for mRCC. As a functional imaging technology, the clinical value of PET/CT has been recognized in diagnosing numerous tumors. In recent years, the application of PET/CT in mRCC has gradually increased. This review focuses on the application of PET/CT in patients with mRCC. In particular, this review discusses the value and limitations of the application of PET/CT in evaluating targeted treatment response and prognosis.