The aim of the study was to assess changes in chosen parameters of sagittal balance of the pelvis in persons with chronic low back pain (CLBP) younger than 64 years and older than 65 years. Total number of randomly chosen hospitalized patients engaged in the study was 152. The patients were divided into 2 groups: persons younger than 64 years (group I, 117 persons, mean age 40.8 years) and older than 65 years (group II, 35 persons, mean age 69.7 years). Radiometric measurements were carried out using radiographs of the pelvis, sacral bone and lumbar spine taken in lateral projections. Results showed that angle A (pelvic angle) was statistically significantly larger in patients from group II (group I – 16°, group II – 21°). Distance D (sacral translation) was also statistically significantly different between groups (group I – 50.3 mm, group II – 61.6 mm). There was no statistically significant difference for angle B (pelvic morphology) (group I – 34.7° and group II –29.3°) and angle C (lumbar lordosis, L1-L5) (group I – 29.2° and group II – 33°). Posterior rotation of the pelvis and sacral bone is often seen in persons with back pain. It is most often accompanied by lumbar hypolordosis, which, together with increase in angle A, could reflect the muscular reaction to pain. Increased angle A and distance D in group of patients older then 65 years was more significance then in youngest one. It can be related with time of duration of back pain or accompany aging of muscles which supporting sagittal balance of the pelvis.