The aim of this article is to describe the main technical differences between multi-slice Computed Tomography (CT) and spiral CT. We also briefly discuss the diagnostic benefits of this new technology which consolidates and expands on the results achieved with spiral CT in the 90s. More specifically, gantry speed and improved spatial resolution in the z axis considerably expand angiographic and cardiac applications, allow high-quality multiplanar and 3D reconstructions, and introduce CT in organ perfusion studies (particularly those of heart and brain).