[Objective - There is no internationally accepted guideline for treatment of spondylolisthesis in the literature, otherwise this degenerative disease has great social and economical impact. There is no hungarian study examining the efficacy of instrumented fusion procedure in surgical treatment of spondylolisthesis. In current study we examined the effectiveness of fusion technique focusing on the impact of quality of life. Methods - Between 1st January, 2011 and 30th June, 2012 we examined a group of patients - who were operated on by instrumented fusion technique because of spondylolisthesis -, in the National Institute of Clinical Neurosciences, using the Oswestry Low Back Disability Questionnaire. All patients were treated after ineffective conservative treatment. The question was wheather how has changed the patients’ quality of life after the operation. Paired-sample t-test was used in this study. Results - Eighty-eight of the 97 examined patients reported different levels of impovement in the postoperative period, two patient’s condition has not changed in spite of the surgery, seven patient’s condition showed progression in average one year after the surgery. The pain improved most significantly (55.5%) (p<0.0001). Using the 16 point borderline according to the Questionnaire (over moderate disability), significant improvement was detected in 50 patients (51.5%). Succesful surgical result - according to the quality of life - was seen in 77.41% of male and in 50.98% of female patients. According to the different age groups, 72.72% of the younger (before retirement), and 53.06% of the retired patients belonged to this group. At least 15 point improvement was detected 35.05% of the patients, the overall improvement was 10.5 point. Discussion - Our results proved effectiveness of instrumented surgical fusion procedure in the treatment of degenerative spondylolisthesis. According to our results the younger male population with significant symptoms is the group, where improvement in quality of life is more pronaunced after the surgical procedure. Conclusion - The instrumented fusion surgical technique provides successful clinical and surgical outcome in patients with degenerative spondylolisthesis. It could improve the quality of life. Althought multicentre follow-up studies are needed to determine the exact indication and optimal therapy.]