Background. Due to the complex etiopathogenesis and the diversity of treatment approaches, spinal pain syndromes constitute a serious medical problem. The chronic pain and functional disturbances accompanying discopathy have motivated a search for more effective physiotherapeutic methods, such as McKenzie’s method of biomechanical diagnosis and treatment and laser therapy. The goal of the present study was to evaluate the analgesic effectiveness of continuous and fractionated doses of laser radiation in chronic lumbo-sacral pain syndrome. Material and methods. Our research involved 88 patients with chronic spinal pain syndrome qualified for McKenzie kinesitherapy. All subjects received kinesitherapy according to the authors’ method, selected according to the biomechanical diagnosis, along with 10 laser therapy procedures. Group A (43 patients) received a continuous dose of 9 J per point, while Group B (45 patients) received a fractionated dose of 3J + 6J per point. 37 points in the lumbo-sacral region were irradiated. Results. Group B showed a significantly greater decrease in pain intensity on the VAS scale (0-10 points), and in pain frequency. Both groups were found to have a reduced deficit in range of movement according to the McKenzie Institute lumbar checklist. Conclusions. Laser therapy with fractionated doses proved to be more effective in pain relief than continuous doses. The method of dosing laser radiation had no effect on improved range of movement in the lumbar spine. Biomechanical treatment using the McKenzie method combined with laser therapy significantly reduces pain and improves the range of movement in patients with chronic lumbar pain syndrome.