To establish systematic diagnosis and treatment planning of dentofacial deformity patient including facial asymmetry or hemifacial microsomia patient, comprehensive analysis of three dimensional structure of the craniofacial skeleton is needed. Even though three dimensional CT has been developed, landmark identification of the CT is still questionable. In recent, a method for correcting cephalic malpositioning that enables accurate superimposition of the landmarks in different stages without using any additional equipment was developed. It became possible to compare the three-dimensional positional change of the maxillomandible without invasive procedure. Based on the principle of the method, a new program was developed for the purpose of diagnosis and treatment planning of dentofacial deformity patient via three dimensional visualization and structural analysis. This program enables us to perform following menu. First, visualization of three dimensional structure of the craniofacial skeleton with wire frame model which was made from the landmarks observed on both lateral and frontal cephalogram. Second, establishment of midsagittal plane of the face three dimensionally, with the concept of "the plane of the best-fit". Third, examination of the degree of deviation and direction of deformity of structure to the reference plane for the purpose of establishing surgical planning. Fourth, simulation of expected postoperative result by various image operation such as mirroring, overlapping.