PURPOSE: To demonstrate a conventional and a new therapeutic method of 3D treatment planning in maxilla tumors, the process of 3D treatment planning and its significance and to compare these two methods. METHOD: We performed 2D and 3D treatment plans. The ADAC planning system was used in the 3D treatment planning. CT and MRI scans were taken on the target volume and on each scan we demarcated the target volume and the critical organs. The irregular fields were obtained by 3D graphic reconstruction provided by the treatment planning programme. RESULTS: Compared to the conventional treatment planning more favourable dose distribution was obtained within the target volume and the radiation burden of the critical organs was kept under their tolerance doses. CONCLUSION: In conformal 3D treatment planning the shape and size of the irradiated volume are in good conformity with those of the target volume. In this way the radiation burden of the critical organs and adjacent intact tissues can be reduced.