The invention relates to a method for displaying the position of a linear instrument (3) navigated with respect to a 3D medical image (1), wherein:- said linear instrument (3) is coupled to a guide (2);- the guide (2) is tracked by a navigation system with respect to the 3D image (1);- a plane (4) passing through the axis of the linear instrument (3) is virtually attached to the guide (2);- a slice reformatted in the 3D image and passing through said plane (4) is displayed.Another object of the invention is a system for carrying out said method.