Objective We aimed to determine the effects of low- and high-energy intensity-modulated radiation therapy(IMRT) photon beams on the target volume planning and on the critical organs in the case of prostate cancer. Methods Thirty plans were generated by using either 6 MV or 15 MV beams separately, and a combination of both 6 and 15 MV beams. All plans were generated by using suitable planning objectives and dose constraints, which were identical across the plans, except the beam energy. The plans were analyzed in terms of their target coverage, conformity, and homogeneity, regardless of the beam energy. Results The mean percentage values of V_(70 Gy) for the rectal wall for the plans with 6 MV, 15 MV, and mixedenergy beams were 16.9%, 17.8%, and 16.4%, respectively, while the mean percentage values of V_(40 Gy) were 53.6%, 52.3%, and 50.4%. The mean dose values to the femoral heads for the 6 MV, 15 MV, and mixed-energy plans were 30.1 Gy, 25.5 Gy, and 25.4 Gy, respectively. The mean integral dose for the 6 MV plans was 10% larger than those for the 15 MV and mixed-energy plans. Conclusion These preliminary results suggest that mixed-energy IMRT plans may be advantageous with respect to the dosimetric characteristics of low- and high-energy beams. Although the reduction of dose to the organs at risk may not be clinically relevant, in this study, IMRT plans using mixed-energy beams exhibited better OAR sparing and overall higher plan quality for deep-seated tumors. Objective We aimed to determine the effects of low- and high-energy intensity-modulated radiation therapy (IMRT) photon beams on the target volume planning and on the critical organs in the case of prostate cancer. Methods Thirty plans were generated by using either 6 All plans were generated by using planning criteria and dose constraints, which were identical across the plans, except the beam energy. The plans were analyzed in terms of Their target coverage, conformity, and homogeneity, regardless of the beam energy. Results The mean percentage values ​​of V_ (70 Gy) for the rectal wall for the plans with 6 MV, 15 MV, and mixedenergy beams were 16.9%, 17.8% and 16.4%, respectively, while the mean percentage values ​​of V 40 Gy were 53.6%, 52.3%, and 50.4%. The mean dose values ​​to the femoral heads for the 6 MV, 15 MV, and mixed-energy plans were 30.1 Gy, 25.5 Gy, and 25.4 Gy, respectively. The mean int egral dose for the 6 MV plans was 10% larger than those for 15 MV and mixed-energy plans. Conclusion These preliminary results suggest that mixed-energy IMRT plans may be advantageous with respect to the dosimetric characteristics of low- and high-energy beams. Although the reduction of dose to the organs at risk may not be clinically relevant, in this study, IMRT plans using mixed-energy beams advantageous for OAR sparing and overall higher plan quality for deep-seated tumors.