A guide means of a centrifugal force separator or cyclone separator for separating at least one substance from a gaseous or liquid medium under the action of centrifugal forces has two or more baffle plates (2) with a radius which decreases from the center axis of the guide means, viewed in the direction of rotation of the medium. Between these baffle plates (2) entry openings (16) into the guide means are formed for the medium from which the substance has been largely removed into the guide means. There is a bottom plate (3) on the end of the guide means which projects into the interior of the device. To improve incident flow or inflow of the medium into the guide means, the bottom plate (3) in the area of the entry openings (16) has recesses (12).