Three-dimensional computed tomographic angiography [CTA], a representative noninvasive radiologic technique, is being widely used for detecting vascular lesions in specific intracranial bleeding under a certain circumstance [acute nontraumatic subarachnoid hemorrhage]. We encountered a case of extravasation of the contrast medium on CTA images that appeared as ribbon-like high-attenuation lesion from an aneurysm at the distal anterior choroidal artery in a young adult moyamoya patient. As CTA is used more frequently, it is imperative to understand such unusual but, potentially lethal image findings to conduct a prompt intervention.