To perform a dosimetric comparison among critical organs using dose-volume histograms (DVH) from 3DCRT, IMRT and Tomo treatment plans for pelvic and para-aortic radiotherapy in post-operative endometrial cancer patients; and to evaluate the integral dose (ID) received by organs within the radiation fields. 10 patients with stage IIIC endometrial cancer were identified from cancer registry and treatment records from 2000 to 2006. Previous radiological datasets were de-archived for this study. For each patient, three plans were created with 3DCRT, IMRT and Tomo. 3DCRT plan was designed to cover planning target volume (PTV) from the T12/L1 border to the bottom of the obturator foramen. Both IMRT and Tomo plans were optimized to keep the mean dose to PTV the same as that of 3DCRT. The prescription was normalized to encompass 95% of PTV at a dose of 50 Gy in 25 fractions for all plans. The ID (the mean dose multiplied by the volume of each structure) for the normal tissue, kidneys, bowel, spinal cord, femurs, rectum, bladder, spine, and pelvic bone was compared with that of 3DCRT plan. V33 (dose received by 1/3 organ volume), V67, and V100 from DVHs of three plans were used for dosimetric comparison for all critical organs, including spinal cord. The mean PTV IDs in the three plans were almost identical (96.5 ± 0.16). Each sample from the 3DCRT plans was designated as 100% and compared with that of IMRT and Tomo. IMRT plans resulted in lower IDs in the bladder, bowel, femurs, kidneys and rectum, ranging from −3.49% to −17.59%. Tomo plans showed similar result except that ID for the bowel raised 0.27%. Both IMRT and Tomo plans increased IDs to normal tissue, pelvic bone and spine in a range of 3.31% to 19.7%. A major disparity was observed in the ID for spinal cord between IMRT (+28.31%) and Tomo (−46.23%). IMRT dosimetry showed excellent coverage of PTV with percent difference of +1.02%, +4.21%, −87.84% and −100% in PTV90 (volume of PTV receiving 90% of the prescribed dose), PTV95, PTV105 and PTV110 respectively. Tomo dosimetry demonstrated marginal improvement of PTV coverage as compared with that of IMRT. Dosimetric comparison with 3DCRT also showed lower V33 and V67, and higher V100 of kidneys, bowel and rectum in both IMRT and Tomo plans. V33, V67 and V100 of bladder and femurs were decreased in both IMRT and Tomo plans except that V100 of femurs was higher in Tomo. V33, V67 and V100 of spinal cord were increased in IMRT (+29.3%, +28.4% and +38.1% respectively) and decreased in Tomo (−45.4%, −54.4% and −25.4% respectively). Both IMRT and Tomo appear to achieve excellent PTV coverage in the extended-field radiotherapy for stage IIIC endometrial cancer compared to 3DCRT. The lower IDs, V33, and V67 in the majority of organs at risk suggest better sparing of these critical structures, but at the expense of increased IDs to normal tissue and skeleton in both IMRT and Tomo plans.