Metastatic castration resistant prostate cancer (mCRPC) is incurable. The expression of the transmembrane protein prostate-specific membrane antigen (PSMA) is markedly increased in most mCRPC lesions. PSMA has been recognized as a viable biologic target for imaging and radionuclide therapy (theranostics) in mCRPC. The PET agents ⁶⁸Ga-PSMA-11 and ¹⁸F-DCFPyL have recently been approved for imaging evaluation of patients with suspected metastasis who are candidates for initial definitive therapy and patients with suspected recurrence based on elevated serum prostate-specific antigen level. Radioligand therapy (RLT) with ¹⁷⁷Lu-PSMA-617 (¹⁷⁷Lu-vipivotide tetraxetan, Pluvicto, Novartis/AAA) was approved on March 23, 2022, based on the favorable results of the VISION trial. It has been recognized that PET imaging of PSMA expression and glucose metabolism (with ¹⁸F-FDG) provides a more comprehensive assessment of the tumor burden and heterogeneity. However, there are many unresolved issues that surround whether or not imaging with ¹⁸F-FDG PET is advantageous in the clinical setting of PSMA RLT in mCRPR.