The invention relates to a problem of setting mutual position of an anatomy being imaged and imaging means of a computed tomography imaging apparatus so that specifically the very volume of the anatomy desired to be imaged actually is imaged. To further the positioning, a positioning tool in a form of a three-dimensional virtual positioning model (40), generated from the anatomy to be imaged, is shown on a display from which the volume (41) of the anatomy desired to be imaged can be pointed, selected or defined.
