A 48-year-old man suffering from paraparesis had congenital kyphoscoliosis due to fused wedged vertebrae between T2 and T4. The kyphoscoliosis consisted of left convex scoliosis measuring 26 degrees and kyphosis measuring 27 degrees. On CT-myelograms and axial MR images, the dura and spinal cord were deviated anterolaterally to the concave side of the curve around its apex. The spinal cord was stuck and flattened against the posterolateral margin of the vertebral body to the base of the pedicle with the posterior subarachnoid space preserved. Anterior decompression from the concave side through a transthoracic approach resulted in a remarkable neurological improvement. The paraparesis may have been caused by compression of the spinal cord through a tethering effect due to its developmental tightness around the apical vertebra and the additional tension created by motions of the neck.