The investigators will image patients with widely metastatic castration-sensitive (CSPC) or castration-resistant prostate cancer (CRPC) using 18F-DCFPyL-PET/CT for detection of tumor burden and perform a lesion-based head-to-head comparison with a subsequent near-term (one to seven days) 18F-DCFPyL-PET/CT follow-up scan, to assess test-retest reproducibility of this second-generation PSMA-targeted compound. Second, as it has not been specifically investigated with this compound before, intra-observer agreement as well as inter-scan variability will be assessed.