Adolescent idiopathic scoliosis (AIS) is associated with osteopenia which could persist into adulthood affecting attainment of Peak Bone Mass thus resulting in osteoporosis in late adulthood. We previously reported a randomized double-blinded placebo-controlled trial(the Cal study) showing significant bone health improvement with 2-year calcium(Ca)+Vit-D supplementation for AIS girls. This study addressed the important issue whether bone health improvement from the initial 2-year Ca+Vit-D supplementation could persist as subjects approached towards Peak Bone Mass at 6-year ie after 4-year of supplement discontinuation. This was an extension of the Cal study on AIS girls (11–14 years old, mean age=12.9 years, Tanner stage<IV) with femoral neck aBMD Z-score<0 and Cobb angle≥15∘. 330 subjects were randomized to Group1(placebo), Group2(600mgCa+400-IU-Vit-D3/day) or Group3(600mgCa+800-IU-Vit-D3/day) for 2-year supplementation after which supplementation was stopped. Investigations at baseline, 2-year and 6-year included High-resolution Peripheral Quantitative Computed Tomography(HR-pQCT) at distal radius and Dual Energy X-ray Absorptiometry(DXA) at both hips. 270(81.8%) subjects completed 2-year supplementation when changes in left femoral neck aBMD, trabecular vBMD, Trabecular BV/TV, Trabecular Number and Trabecular Separation indicated significant bone health improvement with Ca+Vit-D supplementation(p<0.05). At 6-year(mean age=19.2 years), no between-group difference on bone parameters was noted except increase in Cortical Thickness being greater only in Group3 than in Group1. After 4-year supplement discontinuation, the treatment effect from the initial 2-year supplementation mostly dissipated indicating the need of continued supplementation in AIS girls to sustain therapeutic improvement on bone health as subjects approach towards Peak Bone Mass.