Background: the External radiotherapy (EBRT) is the common treatment selection in patients with locally advanced rectum carcinoma. Three-dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) are most techniques used in radiotherapy. However, which one is superior is all controversial. Patients and Methods: thirty-two patients of RC treated with IMRT were selected for current retrospective study. 3DCRT plans were also plan   for all the patients. 3DCRT plans in compared to   IMRT plans were on the basis of planning target volume (PTV) coverage, dose to normal organs, homogeneity index (HI) and conformity index (CI). Results and Discussions:  in both the planning techniques 98% of PTV was covered with more than 96% of prescribed dose. D 95% 15, D 35 and D (Dose to 15%, 35% and 50% volume respectively) for bladder was reduced by 2.09%, 14.623% and 32.57% in IMRT compared to 3DCRT. V (Volume received 45 Gy also volume received 50.4Gy) and in case of bowel doses were found to be better in IMRT than to 3DCRT.  There is significant difference found between doses to both femoral heads in IMRT and 3DCRT. The CI 95% 45 in IMRT plans was found much better than that in 3DCRT whereas HI in both the techniques were found almost same. Conclusion:  IMRT in better significantly in reduction the irradiated of OAR and improved dose conformity in the PTV compared to that by 3DCRT. So, it can be concluded that IMRT should be chosen as best technique for the radiotherapy of Rectum carcinoma