We treated 18 girls for idiopathic thoracolumbar scoliosis with Chêneau brace. The apex of the curve was at Th 12 or at LI or at the disc Thl2/Ll. The initial Cobb angle varied from 21 to 42 degrees, mean 28. The follow up period was of 2 years and 6 months on the average. We noted the rib hump height on Adams' forward bending test. We measured Cobb angle, apical vertebra transposition and apical vertebra rotation (according to Perdriolle method) on antero-posterior standing radiograms before the treatment had started and at the moment of the best correction. We digitized antero-posterior and lateral standing radiograms with sonic digitizer GP-9 and we prepared computed reconstruction of the transversal plane of the spine with Hecquet and Grafs software RACHIS 91TM. The best clinical and radiological correction was achieved after 3 to 8 months of treatment (mean 5,5 months). We considered it as the fitting period and we analysed the correction achieved at that moment and at last follow-up. Cobb angle in brace ranged from 0 to 18 degrees, mean 9 degrees. The correction of apical vertebra transposition ranged from 51 % to 100%, mean 80%. The correction of apical vertebra rotation ranged from 0% to 100%, mean 52%. The correction of rib hump ranged from 0 to 100%, mean 42%. Normal sagittal contour was established in 15 patients. Conclusion: important correction was present in each of the three planes.