Aim. The aim of the study was to examine the dosimetric effect of rectal retraction, using a rectal retractor, by performing a comparative treatment planning study. Material and Methods. Treatment plans using volumetric arc therapy (VMAT) were produced for ten patients both with and without rectal retraction. A hypofractionation scheme of 42.7 Gy in seven fractions was used. The dose to the rectal wall was evaluated for both methods (with and without retraction) using four dose-volume criteria:40.1 Gy , 38.3 Gy , 36.5 Gy , and 32.6 Gy . Results. The retraction of the rectal wall increased the distance between the rectal wall and the prostate. The rectal wall volume was reduced to zero for all dose-volume values except for 32.6 Gy , which was 0.2 cm 3 in average when the rectal retractor was used. Conclusion. There was a significant decrease of 40.1 Gy , 38.3 Gy , 36.5 Gy , and 32.6 Gy when the rectal retractor was used without compromising the dose coverage of planning target volume (PTV).