Background: To study and analyze the variatons in delivered doses to rectum and bladder of carcinoma prostate patents by using kilo Voltage (kV) 'Cone Beam Computed Tomography' (CBCT) images. Materials and Methods: 2-Dimensional kilo Voltage (2D kV) Imaging and CBCT were done for seven prostate cancer patents. The deviatons among their shifts were correlated and the volumetric changes of the rectum and bladder were analyzed. Rectum and bladder contours were redrawn on every boost fractons and dose calculaton were performed on CBCT images to study the effect on dose volume histograms. Results: A correlaton coefficient for set-up variatons was within 0.78 for all directons between CBCT soft tssue matching and kV bone match. The mean deviaton of bladder and rectum volume over the boost fractons was -12% to +9% (SD 31cc to 70cc) and -10.2% to+12% (SD 3.1cc to 14.9cc), respectvely. Bladder mean dose variaton was <1.5Gy for all three positons whereas it was <3.65Gy for rectum. D1% dose deviaton from reference plan for bladder was 1.1Gy (CBCT matched positon), 1.4Gy (kV matched positon), and 1.7Gy (no correcton), and for rectum, the deviatons were 1.2Gy, 2.2Gy, 3.6Gy, respectvely. No significant deviaton was found statstcally significant at the low dose region. Conclusion: It is possible to achieve good dose delivery and conformity in target (prostate) with CBCT image guidance rather than kV bone match, but dose contributon to the rectum is dependent on the patent's anatomy, bladder filling, and rectum filling, pertaining to the day of examinaton. © 2020 Novin Medical Radiation Institute. All rights reserved.