Spontaneous vertebral artery dissection (VAD) has been recognized as being more common than was first thought, with the growing use of magnetic resonance imaging (MRI). However, simple MRI alone is not always satisfactory for making an accurate diagnosis. We experienced two cases of VAD in our clinic, in which three-dimensional computed tomographic angiography (3D-CTA) was performed. Our scanner has the capability of examining a slice of 1mm thick, 0.5mm reconstruction pitch, and a scan time of 1s/rotation. 3D-CTA clearly demonstrated the stenotic change concomitant with the surrounding thrombus and was thought to be useful for making an accurate diagnosis.