The aim of our study was to evaluate the diagnostic effectiveness of a quantitative ultrasound technique for measuring bone tissue at the proximal phalanges of the non-dominant hand. We correlated the mean value of the amplitude-dependent speed of sound (AD-SoS) and the ultrasound bone profile score (UBPS) measured at the phalanges with bone mineral density (BMD) of the lumbar spine gauged with quantitative computed tomography (QCT). We studied a group of 177 postmenopausal women consecutively presenting for osteoporosis screening. We observed that in the whole study group both AD-SoS and UBPS correlated weakly with BMD, although with statistical significance (r = 0.54 and r = 0.45, respectively; p < 0.0001). The same parameters showed a poor correlation (r = 0.48, p < 0.0001; and r = 0.23, p = 0.017) in the group of patients which QCT has classified as osteoporotic. Finally, no correlation was found in the rest of our population. The correlation coefficients of comparison between our QUS and QCT measurements are not strong enough to allow us a prediction of one measure from the other. Therefore, we do not consider the phalangeal osteosonography a valid substitute of QCT technique for assessment of bone status in postmenopausal women.