The link between scoliotic deformity and bone metabolism in adolescent idiopathic scoliosis (AIS) has not been well researched. Moreover, the data concerning the cross-talk between fat tissue content/hormonal activity and bone markers in this group of patients are lacking. The objective of this study was to correlate the extent of scoliotic-curve severity with the bone turnover vs. leptin level and nutritional status in girls with AIS. The study encompassed 77 AIS girls, aged 14.7 ± 2.17 years. Scoliotic curve severity assessed by Cobb’s angle was categorized as mild (10-19o) moderate (20-39º) or severe (≥40º). Corrected height, weight, waist and hip circumferences were measured and body mass index (BMI), corrected height Z-score, BMI Z-score and waist/height ratio (WHtR) were calculated for the entire group. Body composition parameters: fat mass (FAT), fat-free mass (FFM) and predicted muscle mass (PMM) were determined using a bioelectrical impedance analyzer. Bone turnover markers (osteocalcin (OC) and amino terminal of collagen cross-links NTx) and leptin levels were assessed in serum. Multiple regression analysis showed that, OC, NTx (negatively with p<0.05) and leptin (positively with p<0.01) were significantly associated with curve severity in AIS girls. Moreover, Cobb’s angle was positively correlated with W/HtR (p<0.01)and FAT (p<0.05). One-way analysis of variance (ANOVA) revealed significant differences in leptin (p<0.05 vs. mild only), OC (p<0.05 vs. mild and moderate)) and W/HtR (p<0.01 and p<0.05 vs. mild and moderate respectively) between the three AIS severity subgroups. OC was significantly lower in the severe AIS subgroup, while leptin and W/HtR were significantly higher. Significant correlations between leptin and anthropometrical parameters as BMI z-score and W/HtR were shown. Leptin level correlated also significantly with BMI z score (p<0.001), W/HtR (p<0.0001) and body composition parameters (p<0.000001). Moreover, there was a significant negative correlation between NTx and leptin level (p<0.05). Bone metabolism in AIS girls seems to be altered and significantly related to the scoliotic curve severity. Leptin may be a crucial link in the cross-talk between bone turnover and body composition in this group of patients. Further studies concerning this topic are needed.