A method for precision registration of X-ray images to cone-beam CT scan for image-guided radiosurgery includes acquiring 2-D pre-treatment X-ray images of a region of interest, acquiring a 2-D X-ray image of the region of interest at approximately a time of treatment, registering the 2-D X-ray image with a corresponding 2-D pre-treatment X-ray image to obtain a 2-D registration result at approximately the time of treatment, and converting the 2-D registration result into a 3-D tracking result to track the region of interest.