PTH and ibandronate are proven to be effective in reversing negative effects of postmenopausal osteoporosis in terms of bone architecture and density. However, the changes of viscoelastic properties of the bone during the pathogenesis of osteoporosis and its treatment were seldom studied. Thus, this study aimed at studying the viscoelastic changes in PTH and ibandronate treated ovariectomized rat to assess the efficacy of the treatments. In this study, distal femurs of twenty-two female rats from four different groups (SHM, OVX, PTH and IBN) were evaluated using CT, pQCT and nanoindentation tests. While density parameters were well preserved in ibandronate treated group, elastic modulus and hardness were found to be better in PTH treated group. Thus, cortical and trabecular bone could be differentially affected by these two categories of drug, due to their difference in the action of mechanism. Moreover, viscosity of the cortical bone showed a positive correlation (R(2)=0.72) with bone strength predictor SSIy, which would possibly correlate with fracture risk.