Double scoliotic curves usually demand long posterior fusion and limitation of lumbar motion. The purpose of the study was to determine a possibility of one stage surgery, 3D correction, balanced spine and maximum of lumbar mobility. Method: 47 patients in the age of 14±1.6 yrs with double IAS curves were operated from 1995–99 with an average follow up of 50±9 months. Untill 1998 all the patients (31) were fused from Th4 to Th12, leaving the fused curve in balance with compensatory lumbar curve (group1). From 1998–00, 16 patients underwent a single stage anterior surgery of boh curves from Th4-L3 if lower curve averaged 50û (group 2). Two independent observers analyzed the results. Results: G1 (Th 67û±10;L41û±11) was corrected to Th19û±4; L17û±4. Balance changed from 11 mm pre op. to 2.4 mm post op. However, 6 patients (avr. 70û+60û), were corrected to 25û+38û. One year of bracing was necessary to partially correct the disballance, with satisfactory overall results. In 3 patients (Th> 80, L> 50) a balanced spine resulted, but with problematic correction rate. In G2, correction was made from Th68û±17;L63û±10û, to Th23û±12;L21û±8. Mean op. time was 260 min., blood loss 640 ml, post.op. stay 12 days. Conclusion: Fusion down to Th12 showed good results if Th< 80 and L< 50 degrees. In greater curves, an extended single stage fusion down to L3 offered better overall results, better correction, no balance problems and good lumbar mobility.