Ga prostate-specific membrane antigen (PSMA)-HBED-CC PET/CT in a patient with a history of both prostate cancer (PC) and renal cell cancer (RCC) shows high PSMA expression in the residual right seminal vesicle suggestive of local recurrence of PC as well as suspected PSMA-positive mediastinal, retroperitoneal, and iliac lymph nodes. Regarding the latter, biopsy revealed lymph node metastases from RCC excluding PC metastases. This case exemplarily demonstrates that high PSMA expression in RCC metastases can potentially mimic PC metastases. Thus, for accurate interpretation of imaging results in PC patients with additional primary tumors, knowledge of PSMA expression of non-PC tissue is necessary.