This paper reports a retrospective longitudinal study of patients with documented progressive adolescent idiopathic scoliosis (AIS) or with scoliosis associated with cerebral palsy (SACP) to determine the relative amount of wedging between vertebrae and discs as a function of progression of the scoliosis curve and curve region. It was found that 1. the curves in SACP patients were longer, and more commonly in the thoraco-lumbar region; 2. The relative vertebral and disc wedging was not significantly different between curves early and late in the progression in either group; 3. In AIS, thoracic curves (King II) the vertebrae were more wedged than the discs, the converse was found in the lumbar curves (King I); 4. A similar difference by anatomical level was found in SACP curves, with the thoraco-lumbar curves resembling lumbar curves rather than thoracic.