The authors describe an anterior decompression procedure for thoracic ossification of the posterior longitudinal ligament (PLL) in which they used an image guidance system in three cases. To make registration possible in anterior thoracic surgery, they devised a surgical reference frame that could be connected to a rod and attached to an external fixation device, which was then attached to the thoracic VB. The mean fiducial error at the registration was acceptable (range 0.5-0.8 mm). They were able to confirm the success of decompression on postoperative computerized tomography scans. In the removal of an ossified thoracic PLL, an image guidance system has been shown to be a useful tool.