METHODS Prospective cohort study. OBJECTIVE To evaluate the contribution of upper and lower lumbar segments to flexion and extension of the lumbar spine in normal and diseased spines. BACKGROUND The specific contributions of upper and lower lumbar segments during flexion/extension have rarely been reported. Furthermore, no comparisons between the flexion/extension behaviors of normal and diseased spines have been reported until now. METHODS Flexion and extension lateral radiographs of 52 adult, asymptomatic volunteers, and 67 adult patients with lumbar spine disc disease were measured using software for total lumbar lordosis, upper lumbar lordosis and lower lumbar lordosis and the intervertebral angles of all segments. RESULTS In asymptomatic volunteers, the range of movement between flexion and extension was a mean of only 4.2° in the lower lumbar spine and a mean of 19.4° in the upper lumbar spine. In patients with disc degeneration, the range of movement between flexion and extension was an average 6.5° for lower lumbar spine and 15.6° for the upper lumbar spine. CONCLUSIONS The results showed that upper lumbar spine contributes more to the range of motion in flexion and extension than the lower lumbar spine in asymptomatic individuals without lumbar disc disease, as well as in patients with disc degeneration.