Although three-dimensional computed tomographic angiography was developed as a screening tool for use in patients with suspected cerebrovascular disease, this imaging modality has also proven to be of value in surgical planning for patients with large or unusual vascular lesions of the brain. The three-dimensional images generated by this technique yield valuable information regarding the size and configuration of intracranial aneurysms and vascular malformations, the presence and extent of intra-aneurysmal thrombus, the relationship of the vascular lesion to other cerebrovascular or skeletal structures, aneurysm wall thickness, and the presence and orientation of an aneurysm neck. The use of three-dimensional computed tomographic angiography in representative cases of patients with large or unusual cerebrovascular lesions is presented. It has been our experience that this imaging modality displays anatomical information that is not readily available from standard, intra-arterial angiography, provides better detail for surgical planning than magnetic resonance angiography, and is less expensive than either of these other imaging modalities.