Purpose: 18F-​Fluorocholine (FCH) and 11C-​acetate (ACE) PET are widely used for detection of recurrent prostate cancer (PC)​. We present the first results of a comparative, prospective PET​/CT study of both tracers evaluated in the same patients presenting with recurrence and low PSA to compare the diagnostic information provided by the two tracers. Methods: The study group comprised 23 patients studied for a rising PSA level after radical prostatectomy (RP, 7 patients, PSA ≤3 ng​/mL)​, curative radiotherapy (RT, 7 patients, PSA ≤5 ng​/mL) or RP and salvage RT (9 patients, PSA ≤5 ng​/mL)​. Both FCH and ACE PET​/CT scans were performed in a random sequence a median of 4 days (range 0 to 11 days) apart. FCH PET​/CT was started at injection (307 ± 16 MBq) with a 10-​min dynamic acquisition of the prostate bed, followed by a whole-​body PET scan and late (45 min) imaging of the pelvis. ACE PET​/CT was performed as a double whole-​body PET scan starting 5 and 22 min after injection (994 ± 72 MBq)​, and a late view (45 min) of the prostate bed. PET​/CT scans were blindly reviewed by two independent pairs of two experienced nuclear medicine physicians, discordant subgroup results being discussed to reach a consensus for pos., neg. end equivocal results. Results: PET results were concordant in 88 out of 92 local, regional and distant findings (Cohen's kappa 0.929)​. In particular, results were concordant in all patients concerning local status, bone metastases and distant findings. Lymph-​node results were concordant in 19 patients and different in 4 patients. On a per-​patient basis results were concordant in 22 of 23 patients (14 pos., 5 neg. and 3 equivocal)​. In only one patient was ACE PET​/CT pos. for nodal metastases while FCH PET​/CT was overall neg.; interestingly, the ACE-​pos. and FCH-​neg. lymph nodes became pos. in a second FCH PET​/CT scan performed a few months later. Conclusion: Overall, ACE and FCH PET​/CT showed excellent concordance, on both a per-​lesion and a per-​patient basis, suggesting that both tracers perform equally for recurrent prostate cancer staging.