Controversy exists regarding the use of bilateral hip scanning. The reason for scanning unilaterally might be the reporting of good correlation between BMD of the hips. As the diagnostic classification in most cases is solely based on the lowest T-score of the spine or hip, the interpretation might be affected by significant left-right difference in hip BMD, especially in the old. The purpose of our study was to ascertain the difference in BMD measurement of the two hips in a population of Caucasian community dwelling women older than 65 years invited for screening. We found that bilateral BMD measurements were only moderately correlated at the femoral neck and total hip. In a significant number of the screened elderly women, we found that the DXA differences changed the diagnosis of each woman from either normal BMD to osteopenia or visa versa or from osteopenia to osteoporosis or visa versa. We found an increasing difference between the hips with increasing age and this difference was up to 9.1% in the women older than 70 years when evaluating femoral neck, meaning that the diagnosis of osteoporosis in a subset of patients would depend on whether the left or right hip was scanned. When evaluating total hip, the disagreement was somewhat lower (6.0%) in women aged superior to 70 years. Our study is the first to show this age dependency. In conclusion, due to increasing BMD difference between hips with increasing age, bilateral hip measurements should be performed in elderly women aged 65 years or more.