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Object. To identify the importance of main risk factors of early development of degenerative changes in adjacent spinal mo- tion segments after the lumbar fusion. Material and Methods. The study evaluated the treatment results in 354 patients who underwent fusion in the lumbar spine for degenerative-dystrophic disease. Two groups were compared: Group I included 26 patients with clinically significant adjacent segment disease (ASD) which developed during the first year after surgery, and Group II – 24 patients in whom ASD was identified at a later date. Results. Significant degenerative changes in the overlying intervertebral disc (Pfirrmann grade 4 and higher) were found preoperatively in 16 (61.5 %) patients in Group I. In Group II, such degenerative changes were observed in 3 (12.5 %) pa- tients. Besides, patients in Group I had higher mean index of the difference between pelvic inclination and lumbar lordosis (PI-LL), than patients in Group II (12.2° and 9.3°, respectively). Nine patients in Group I with Pfirrmann grade 4 to 8 de- generative changes demonstrated sagittal imbalance as Positive in 7 cases and Very Positive in 2 cases, according to Schwab classification. Conclusion. Decompensation of the pre-existing degenerative changes in the conditions of increased load after fusion is cru- cial in early development of the adjacent segment disease. Patients with degenerative changes in the adjacent levels of grade 4 and higher according to Pfirrmann, as well as patients with PI-LL index more than 11° have a significantly higher risk of early ASD development.