This study was designed to evaluate the personality characteristics of orthognathic surgery patients preoperatively and postoperatively through the MMPI. Comparison was made between the personality characteritics of preoperative and postoperative groups. Motivation for undergoing orthognathic surgery and postoperative satisfaction were examined through the questionnaire. Subjects used in this study consisted of 50 patients under presurgical orthodontic treatment and 22 patients who had received orthognathic surgery. From this study, the results were followings. 1. In preoperative patients group, all T-scores were within the normal range except for K-scale. The T-score of K-scale is 57.7, this showed that these patients underwent some or less stress. 2. In postoperative patients group, all T-scores were within the normal range. 3. Only in K-scale, there was statistically significant increase after surgery (P<0.05). 4. In male patients group, all T-scores were within the normal range except for that of preoperative K-scale. Postoperatively, there were statistically significant increase in K and Hs scales(P<0.05) 5. In female patients group, all T-scores were within the normal range. 6. Motivation for undergoing orthognathic surgery could be divided into 4 categories. : esthetic goal(28.2%), functional goal(32.1%), TMJ problem(9.0%), and psychosocial reason(30.7%). 7. The degree of postoperative satisfaction was quite high(85.7%). 14.3% of all patients were very satisfied, 71.49/o were satisfied, 9.5% were neither satisfied or dissatisfied, and 4.8% were very dissatisfied.