The third-dimension of scoliosis represent a great challenge for clinicians used to think in two dimensions due to the classical radiographic representation of the deformity. This caused problems in everyday clinical approaches, and led to the development of new bidimensional classifications (King, Lenke) who tried in different ways to face these problems, mainly in a surgical perspective. Recently, some three-dimensional classifications have been proposed, all developed in laboratory by bioengineers. In this paper we present the existing classifications of scoliosis, both bi-dimensional and three-dimensional and we thoroughly discuss the 3-DEMO (3-D Easy Morphological) that has been first presented years ago, and recently thoroughly published; this classification has been developed by clinicians with the main aim of being understandable and easily applicable to everyday clinical life.