Type 2 diabetes mellitus (T2DM) is associated with a higher risk of fractures even in presence of normal or increased bone mineral density. The purpose of this three-year longitudinal study was to evaluate the risk of osteoporotic fractures by assessing the changes of Quantitative Ultrasound (QUS) parameters in a group of postmenopausal women with type 2 diabetes mellitus (T2DM) compared with non-diabetic controls. The measurements were taken on a group of 18 postmenopausal women affected by T2DM and 18 healthy age-matched controls, aged 55-70 years, referring to the Osteolab laboratory at the ISBEM Research Institute (Brindisi, Italy) between 2009 and 2013. Subjects had baseline and 3-year follow-up measurements with phalangeal QUS carried out by a DBM Sonic Bone Profiler 1200 (Igea®); medical history, current drug therapies and risk factors for fractures were recorded for each patient. The analyzed phalangeal QUS parameters were Amplitude-Dependent Speed of Sound (AD-SoS), Bone Transmission Time (BTT), Fast Wave Amplitude (FWA) and Signal Dynamic (SDy). At the baseline visit we found no statistically significant difference between T2DM and non-diabetic patients when looking at phalangeal QUS parameters. At the three-year follow-up visit, a significantly higher decrease of both BTT (P<0.001) and AD-SoS (P<0.001) parameters was found in the T2DM group. On the contrary, the decrease of FWA was significantly higher in non-diabetic controls (P<0.001). Our data confirm the ability of phalangeal QUS to detect differences in the risk of osteoporotic fractures in T2DM postmenopausal women compared to non-diabetic controls. The study suggests that T2DM women present a higher cortical porosity and increased trabecular bone density compared to non-diabetic controls, respectively shown by the higher decrease of both AD-SoS and BTT and the lower decrease of FWA.