A method for defining scanning parameters of a CT scan of a region of interest of an examination object (O) using a CT system is described. In an embodiment of the method, external image capture of external features of the examination object is carried out using an additional image capture unit. In addition, at least one scanning parameter in the axial direction of the CT system is determined on the basis of the external image capture. Finally, a CT scan is performed using the at least one scanning parameter determined. A CT scan range defining device is additionally described. A computed tomography system is also described.
