OBJECTIVE Some observations indicate that GH deficiency (GHD) may have little impact on bone mineralization in contrast to its effects on bone growth and maturation. The aim of the present study was to evaluate the effects of isolated GHD and GH-replacement therapy on bone quality assessed by a quantitative ultrasound (QUS) technique at the proximal phalanges of the hand. DESIGN Growth and QUS data of 68 subjects (50 males and 18 females) aged 5-18 yr with isolated GHD were retrospectively examined. A cross-sectional series of 120 observations was collected and compared with data obtained from a control population (1227 healthy children, 641 males and 586 females, aged 3-16 yr). METHODS QUS variables amplitude- dependent speed of sound (AD-SoS) and bone transmission time (BTT) were assessed by the sonographic device DBM Sonic BP IGEA. Height and weight measurements were performed according to standard techniques. In patients, skeletal age (SA) was determined by Tanner-Whitehouse method (3rd version). RESULTS Before treatment height, SA, ADSoS and BTT were reduced in patients. Height SD score (SDS), SA SDS, AD-SoS SDS, and BTT SDS improved during treatment. Significant associations of both AD-SoS and BTT with age, SA, height, and therapy duration were observed. Using multivariate regression models the disease state, SA, and height proved to be significant variables in predicting BTT and AD-SoS. CONCLUSIONS QUS measurements adjusted for body size and skeletal maturity in GHD patients seem to be only slightly reduced. A body size and skeletal maturity adjustment should be incorporated in studies on bone mass in GHD children and adolescents. A non-invasive technique such as QUS technology opens new perspectives.