Scoliosis is a three-dimensional deformity caused by the lateral tilt and rotation of the vertebrae, resulting in a angulation of minimum 10°. In addition to the cosmetic aspect of the deformity, more severe curves are often accompanied by social life problems, lower marriage and higher divorce rates, fewer children per marriage, eating disorders, increased psychiatric consultations, and increased suicide rates. The aims of surgical treatment are to correct coronal, rotational and chest wall deformities, to provide global sagittal balance and to achieve a solid fusion. Preservation of as many mobile segments as possible, especially in the lumbar spine, and improvement in pulmonary functions are other goals of surgery. Discussions continues about when surgery should be performed. Although a high rate of complications are observed in surgery performed at a very early age, the deformity may not be satisfactorily corrected in surgery performed at a later age. The skeletal maturity level of the patient is one of the primary determinants of the time of surgery. In this article, pre-surgical evaluation, in which case and when surgery should be performed are presented together with literature information.