Children with GH deficiency have reduced bone mass and mineral density in comparison with normal individuals. GH treatment improves the accrual of bone mass during childhood and adolescence, but suboptimal GH treatment may cause a reduced bone mass in adulthood. At final height, treated patients with GH deficiency have normal mean values of bone mass, but some patients showed reduced lumbar bone mineral density (BMD) values. Lumbar peak bone mass (PBM) in treated patients who discontinued the treatment at final height is delayed and reduced. GH treatment during the transition from late adolescence to young adulthood can increase bone mass and mineral density. In patients with GH deficiency a possible strategy for avoiding acquisition of a suboptimal bone mass in the young-adult, could be to continue GH treatment during the transition to adulthood up to the acquisition of PBM.