In its first-in-human application in a patient with prostate cancer and biochemical recurrence, [89Zr]-PSMA-DFO PET (48 h p.i.)showed local recurrence (SUVmax 13.25) that was equivocal (SUVmax 5.37) on [18F]-labeled PSMA PET ([18F]-JK-PSMA-7) at 2 h p.i. This indicates the potential advantage of [89Zr]-PSMA-DFO PET for localizing tumors with low PSMA expression. The gene discussed is FOLH1; the disease is prostate cancer.