The values of bone density represent one of the best parameters for the prediction of the risk of fracture in the adult. Since the peak of bone mass depends over that on genetic factors also on modifiable environmental factors, the evaluation of the state of bone health in paediatric populations has assumed great importance; the ultrasound techniques seem to represent a potential alternative to DXA and QTC. Using Omnisense device (Omnisense, Sunlight Ultrasound Technologies) we have evaluated the bone strength in a champion of 652 children and teen-agers aged 6-18 (328 females, 324 males). The measurements have been made at the distal third of the radius and midshaft tibia. The purpose has been to record the values of SOS in a healthy paediatric population, building a normal database and to find a correlation between the SOS values and anthropometric data, dietary factors and physical activity. The comparison with an analogous study conducted by other Authors prompted us to conclude that in the paediatric population the construction of proper curves of reference, with which to compare the data of the patients, is essential to avoid errors in the evaluation of bone density, in agreement with how much already underlined in literature. Besides a correct interpretation of the data obtained with ultrasounds systems asks for a change of the thresholds values established by the OMS for the diagnosis of osteopenia/osteoporosis with the DXA. As already happened for the adult population in children also it will be therefore necessary to compare a great number of pathological subjects with the normal database, establishing so the new values of Z-Score and giving a clinical meaning to the effected measurements.