An in vivo study investigated 2D and 3D relationships between global and local vertebral and discal descriptors of the scoliotic spine deformity. It was performed on a cohort of 40 patients representing a wide range of thoracic curve progression. Global descriptors referred to Cobb angle in PA view as well as corresponding Cobb angle in the plane of maximum deformity and its angular orientation. Local descriptors included vertebral axial rotation, wedging angles in the global and local vertebral frontal planes as well as a 3D maximum wedging angle and its angular orientation. Statistical analyses indicated that, at the thoracic level, vertebral wedging and axial rotation increase with curve severity. The 3D maximum wedging tends to shift towards the left posterolateral vertebral region with curve severity, with simultaneous displacement of the plane of maximum deformity toawrds the coronal plane. These results confirm the importance of 3D measurements in the understanding of biomechanics of idiopathic scoliosis.