Measurement of bone mineral status may be a useful tool in identifying the children who could be exposed to an increased risk of osteoporosis in adulthood. Dual energy x-ray absorptiometry and peripheral quantitative computed tomography may be used to this purpose, but the exposure to ionizing radiation is a limiting factor for preventive studies in large populations of children. In the last years, quantitative ultrasound (QUS) methods have been developed to assess bone mineral status in some peripheral skeletal sites such as calcaneus, phalanges of the hand, and tibia. QUS techniques are safe, easy to use, radiation-free, and devices are portable, so that they are particularly indicated to assess bone mineral status in children. This review will concentrate on the main methodological principles of ultrasounds and the QUS variables derived from their application to bone tissue, technical differences and performance of QUS methods, factors influencing QUS measurements, normative data and results obtained in children with disturbances of growth or affected by disorders of bone and mineral metabolism, including the assessment of fracture risk, and comparison among QUS, dual energy x-ray absorptiometry, and peripheral quantitative computed tomography methods.