In order to evaluate spinal deformities in scoliosis, a new non-ionising technique has been adopted. This technique allows to measure the 3D spatial positions of small unobtrusive hemispheric passive markers placed on anatomical repere points. After having acquired the raw data, a very sophisticated signal processing algorithm, that will be described herein after, has been developed in order to obtain from the measurements of the spine landmarks, the extraction of clinical parameters related to those usually calculated on the radiographic image. The implemented procedure is completely automatic, insensible to edge effects, applicable to short data sets, reliable in filtering and derivative assessment and fast. Various examples of the results obtained of various analysed subjects showing the algorithm reliability and clinical efficacy are presented.