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Androgen deprivation therapy (ADT) puts patients at an increased risk of developing osteoporosis. Assessment of bone mineral density (BMD) is most commonly performed by dual energy X-ray absorptiometry (DXA). Alternative ways of estimating BMD, such as quantitative ultrasound (QUS) measurement of the heel, are explored as DXA is expensive, non-portable and uses ionising radiation. We therefore investigated the diagnostic value of QUS as compared with DXA in patients commencing ADT.In this cross-sectional study of 60 patients with prostate cancer who were about to start ADT, BMD was measured with DXA and QUS. The fracture risk score, as implemented by the Dutch National Osteoporosis Guideline, was also measured.No significant correlations were found between the separate DXA T scores and worst DXA T score, and the QUS T scores. Correlations between DXA T scores/QUS scores and fracture risk score were also non-significant. If QUS had been used as a screening tool, with a threshold of T ≤ -0.5 to perform DXA, then relevant osteopenia/osteoporosis (worst DXA T score ≤ -2.0) would have been missed in 1/18 (5.6%) patients. The negative predictive value is 0.95. Using QUS as a screening test prior to DXA and a QUS threshold T score ≤ -0.5 would avoid 21 (35%) DXA scans at the cost of missing one (5.6%) case.QUS testing cannot replace DXA scans fully as a diagnostic test. However, QUS can be incorporated as triage test prior to DXA to reduce the need for unnecessary DXA scans and the associated costs.