The purpose of this study is to evaluate the relationship between osteoporotic postmenopausal women and its bone mineral density value by using the single energy quantitative CT. 1. Decreasing BMD with age is evident. There is a significant low BMD value in the osteoporotic women compared with the healthy subgroup. 2. BMD decrease from T12 to L4, except in healthy premenopausal women. 3. Relationship of spinal BMD expressed as average BMD of T12 through L4 Show strong correlation with mean BMD in all vertebral levels. 4. There are significantly different BMD value from T12 through L4 in subgroup 1, 2, 3 but there is no statistically significant difference between subgroup 2 and 3. Conclusion, There is a significant decreasing BMD with age but it is difficult to differentiate postmenopausal relatively healthy women from osteoporotic women by BMD.