Aim. To assess the effectiveness of the long-term group psychotherapy in war veterans with posttraumatic stress disorder (PTSD) by evaluation of clinical picture of PTSD, associated neurotic symptoms and adopted models of psychological defense mechanisms. Methods. Prospective cohort study of 59 war veterans who participated in a five-year dynamic-oriented, supportive group psychotherapy. The groups met once a week for 90 minutes. Forty-two veterans finished the psychotherapy. The Clinician Administered PTSD Scale structured interview was used to assess the intensity of PTSD, Crown-Crisp Index was used to assess other neurotic symptoms, and Life Style Questionnaire was used to assess the defense mechanisms. The assessments were done at the beginning of psychotherapy, after the second, and after the fifth year of treatment. Comorbid diagnoses, hospitalizations, and treatments in a day hospital were observed. Results. Long term group psychotherapy reduced the intensity of PTSD symptoms (difference between CAPS score at the beginning and end of treatment F=9.103 P=0.001). Other neurotic symptoms and the characteristic profile of defense mechanisms did not change significantly during the course of treatment. Predominant defense mechanisms were projection (M=82.0± ; ; ; 14.4) and displacement (M=69.0± ; ; ; 16.8). No symptom or defense mechanism showed significant difference at the beginning of treatment, after two and after five years of treatment. After the second year of psychotherapy, the number of diagnosed major depressive episodes increased, and decreased at the end of treatment. Conclusion. Psychotherapy can reduce the intensity of PTSD symptoms, but the changes in the personality of veterans with PTSD are deeply rooted. Traumatic experiences lead to forming of a rigid model of defense functioning, which, unfortunately, can hardly be significantly influenced by long term group psychotherapy.