The aim of this study was to provide reference standards for measurements of quantitative ultrasonography (QUS) of radius and tibia in normative Greek pediatric population. Analysis was performed in 1549 healthy subjects (814 girls and 735 boys) with a mean decimal age of 11.41+/-3.52 yr (range: 3.78-18.33 yr). Results showed a gradual increase of absolute values of radial and tibial speed of sound (SOS), with aging and with pubertal progressing, in both girls and boys. Gender comparison showed significantly increased SOS values measured both at radius and at tibia in girls more than 13 yr of age compared with aged-matched boys. Significant but mild correlation was noted between standard deviation scores (SDS) of SOS at radius and at tibia (r = 0.259, p < 0.001). Additionally, tibial SOS SDS were significantly negatively correlated with body mass index (BMI) SDS (r = -0.230, p < 0.001). Finally, subjects that spend more than 3h of daily "screen time" (television and personal computer) showed significantly decreased SOS values measured both at radius and at tibia. On the contrary, no correlation was observed between SOS values and the amount of physical activity reported.