Introduction The goal of this study is to determine the best treatment technique for prostate cancer treatments depending on various patients repositioning methods. Material and methods Five patients treated for localized prostate cancer to a total dose of 60 Gy in 15 fractions were enrolled in this study. For 6 treatment fractions, different repositioning methods (tattoos, bones, fiducial markers, and organs) were simulated. Plans were calculated on CBCT for each method and treatment technique: conformal 6 fields with various PTV margins, IMRT and VMAT. Dose calculation on CBCT, respect to CT, was estimated to be correct within 2%. Approximately 500 DVHs for PTVs and rectum were obtained. Integrated doses for target volumes and rectum for each couple of treatment technique versus positioning method were calculated. An optimization function using weights for the integral doses of PTVs and rectum was created to find the best compromise between target coverage and rectum sparing. Results Conformal 6 fields plan, with PTV margins of 3 mm, was the best technique, when re-calculating the dose on the daily CBCT image with newly delineated organ contours. Unless we give considerable weight to the rectum, all other techniques appeared inferior with in particular repositioning on tattooed points to proscribe. VMAT plans simply re-calculated with no optimization on newly delineated organs but with repositioning on CBCT was the second treatment option. Conclusions The results showed clearly that a conformal 6 beams plan with reduced margins based on daily redefined contours on each CBCT is an excellent treatment choice. On-line adaptive planning for this technique would be fast enough to avoid patient's internal organ movements, without need of pre-treatment QA on phantoms, therefore feasible and superior to a dose modulated plans not adapted to daily organ motion. It is obvious that the best choice depends on department technical possibilities, on the staff organization as well as patients’ acceptance of invasive acts (installation of fiducial markers, spacer, purging, etc.). Nevertheless an advanced treatment technique (IMRT/VMAT) is not necessarily the best choice. The goal of this study is to determine the best treatment technique for prostate cancer treatments depending on various patients repositioning methods. Five patients treated for localized prostate cancer to a total dose of 60 Gy in 15 fractions were enrolled in this study. For 6 treatment fractions, different repositioning methods (tattoos, bones, fiducial markers, and organs) were simulated. Plans were calculated on CBCT for each method and treatment technique: conformal 6 fields with various PTV margins, IMRT and VMAT. Dose calculation on CBCT, respect to CT, was estimated to be correct within 2%. Approximately 500 DVHs for PTVs and rectum were obtained. Integrated doses for target volumes and rectum for each couple of treatment technique versus positioning method were calculated. An optimization function using weights for the integral doses of PTVs and rectum was created to find the best compromise between target coverage and rectum sparing. Conformal 6 fields plan, with PTV margins of 3 mm, was the best technique, when re-calculating the dose on the daily CBCT image with newly delineated organ contours. Unless we give considerable weight to the rectum, all other techniques appeared inferior with in particular repositioning on tattooed points to proscribe. VMAT plans simply re-calculated with no optimization on newly delineated organs but with repositioning on CBCT was the second treatment option. The results showed clearly that a conformal 6 beams plan with reduced margins based on daily redefined contours on each CBCT is an excellent treatment choice. On-line adaptive planning for this technique would be fast enough to avoid patient's internal organ movements, without need of pre-treatment QA on phantoms, therefore feasible and superior to a dose modulated plans not adapted to daily organ motion. It is obvious that the best choice depends on department technical possibilities, on the staff organization as well as patients’ acceptance of invasive acts (installation of fiducial markers, spacer, purging, etc.). Nevertheless an advanced treatment technique (IMRT/VMAT) is not necessarily the best choice.