Background: Generally, scoliotic girls have a tendency to lean further back than a comparable group of non-scoliotic girls. To date, no study has addressed how standing balance in untreated scoliotic girls is affected by a natural backwardly or forwardly inclined trunk. Methods: 27 able-bodied young girls and 27 young girls with a right thoracic curve were classified as leaning forward or backward according to the median of their trunk sagittal inclination. Participants stood upright barefoot. Trunk and pelvis orientations were calculated from 8 bony landmarks. Upright standing balance was assessed by 9 parameters calculated from the excursion of the center of pressure and the free moment. Findings: In the anterior-posterior direction, backward scoliotic girls had a greater center of pressure range (P=0.036) and speed (P=0.015) by 10.4mm and 2.8mm/s respectively than the forward scoliotic group. Compared to their matching non-scoliotic group, the backward scoliotic girls stood more on their heels by 14.6mm (P=0.017) and display greater center of pressure speed by 2.5mm/s (P=0.028). Medio-lateral center of pressure range (P=0.018) and speed (P=0.008) were statistically higher by 8.7mm and 3.6mm/s for the backward group. Only the free moment RMS was significantly larger (P=0.045) for the backward scoliotic group when compared to the forwardly inclined scoliotic group. Interpretation: Only those with a backward lean displayed statistically significant differences from both forward scoliotic girls and non-scoliotic girls. Untreated scoliotic girls with an exaggerated back extension could profit more from postural rehabilitation to improve their standing balance.