Abstract: A filter includes a filter element (1) having a filter medium (106) pleated in a zigzag manner, with a raw side (105) and a clean side (104). Filter medium sections (120) extend on either side of the raw-side pleat tips (102a) to adjoining raw-side pleat bases (103a) include a first bend (552) toward the raw side (105), and behind that a second bend (554) toward the clean side (104). A plurality of elongated depressions (656) are formed on the raw side (105), which extend between pleat tips (102a) and pleat bases (103a) approximately perpendicular to pleat edges (F) and implement corresponding elevations (658) on the clean side (104) such that, in a raw-side pleat intermediate space (148a), in each case, two depressions (656) on the two medium sections (120) delimiting the pleat intermediate space (148a) are located directly opposite of each other and each form a flow channel (660).