Objectives:This study was designed to investigate the characteristics of personality changes and emotional distress using the Personality Assessment Inventory (PAI) in patients with traumatic brain injury(TBI), divided into mild (MTBI) and severe (STBI) groups according to the severity of injury. Methods:The subjects were consisted of 25 patients with MTBI, 25 patients with STBI, and 25 normal controls. They were interviewed with the PAI. The data were analyzed by ${chi}^2$ test, analysis of variance and Tukey test. Results:The results were the followings. First, Negative Impression in validity scales was elevated above cutoff point(T score 70) in both MTBI and STBI groups. Second, the clinical scales of which scores elevated above the cutoff point were Somatic Complaints, Anxiety, Anxiety-Related Disorders, Depression, and Schizophrenia in the MTBI, and Somatic Complaints and Depression in the STBI. Third, the clinical subscales above the cutoff point were Conversion, Somatization, Health Concerns, Affective Anxiety, Physiological Anxiety, Traumatic Stress, Cognitive Depression, Affective Depression, Physiological Depression, Thought Disorder, and Affective Instability in the MTBI, and Health Concerns, Cognitive Depression, Affective Depression, and Physiological Depression in the STBI. Fourth, Suicide Ideation in treatment scales was the only scale above the cutoff point in the MTBI and the others of the treatment and interpersonal scales in the MTBI and all of these scales of the STBI were not elevated above the cutoff point. Fifth, the scales of which scores showed significant difference between the MTBI and the STBI were Somatic Complaints, Anxiety, Depression, and Suicide Ideation, the subscales were Conversion, Somatization, Health Concerns, Affective Anxiety, Physiological Anxiety, Physiological Depression, and Psychotic Experiences. Conclusion:These results suggest that the patients with MTBI had more somatic and anxiety symptoms, depressed mood, and suicidal ideation than the patients with STBI. These characteristics are generally consistent with clinical observation and findings from previous studies of the patients with TBI, and the PAI seems to be a beneficial adjunctive assessment tool for the evaluation of patients with traumatic brain injury.