A device and a method for planning an endovascular procedure are proposed. A medical instrument, particularly a catheter, is introduced into a vessel and is guided to its place of application via the vessel. Vessel diameters and bend radiuses along a plotted vessel course are automatically determined from the volume data set of the medical imaging and compared with a maximum diameter and minimum bend radius of the medical instrument planned for use. Points or regions within the plotted vessel course which have too low a vessel diameter or bend radius are subsequently highlighted in color in an image display of the vascular tree or vessel course. The user immediately detects critical areas and can if necessary change his or her plan or resort to an instrument with different geometric data. The method and the device make planning the endovascular procedure possible even for inexperienced users.