To justify CT purchases and document certificates of need, the clinical effectiveness of CT scanners with different cost and resolution must be compared. The diagnostic accuracy and anatomic detail in three scanners with different resolution were studied. Seventeen patients were studied with both a first or a second generation CT scanner and a third-generation scanner. Appearance of normal and pathologic structures was compared. Cerebral sulci, corticomedullary discrimination, basal cistern vessels, and some pathologic lesions were seen in third generation images that were not seen in the others. Higher resolution scans provide significantly better anatomic detail and accuracy in detecting pathologic processes.