Illumination device for vehicles with a flat light-conducting element, - which has opposing flat sides at which light coupled in is totally reflected, - which has a first narrow side in a light coupling-in area for coupling in the light, - which has a second narrow side in a light coupling-out area for coupling out the light in the main radiation direction of the illumination device, - which has a connecting side (13, 14) joining the first narrow side and the second narrow side, - that an elongated optical waveguide is provided, which follows the contour of the first narrow side of the flat light-conducting element and has a first end face arranged at the end and a second end face between which an outer surface of the elongated optical waveguide extends, which has coupling-out elements for deflecting the light coupled into the elongated optical waveguide, so that the light is coupled out of the elongated optical waveguide in the direction of the first narrow side of the flat light-conducting element by a longitudinal section of the outer surface towards the first narrow side of the flat light-conducting element, - that the flat light-conducting element is not designed to be level, - and that the flat light-conducting element rises from a base plane spanned by an extension plane (E 1) of the second narrow side and a main radiation direction in the direction of a rear corner region of the light guiding element, said corner region being arranged on a side facing a body end edge, and - that the first narrow side is twisted by a twist angle (φ 1) in the direction of the corner region relative to an extension line (E 3) of the first narrow side and/or the connecting side is twisted by a twist angle (φ 2) in the direction of the corner region relative to an extension line (E 2) or the connecting side. - which has opposing flat sides at which light coupled in is totally reflected, - which has a first narrow side in a light coupling-in area for coupling in the light, - which has a second narrow side in a light coupling-out area for coupling out the light in the main radiation direction of the illumination device, - which has a connecting side (13, 14) joining the first narrow side and the second narrow side, - that an elongated optical waveguide is provided, which follows the contour of the first narrow side of the flat light-conducting element and has a first end face arranged at the end and a second end face between which an outer surface of the elongated optical waveguide extends, which has coupling-out elements for deflecting the light coupled into the elongated optical waveguide, so that the light is coupled out of the elongated optical waveguide in the direction of the first narrow side of the flat light-conducting element by a longitudinal section of the outer surface towards the first narrow side of the flat light-conducting element, - that the flat light-conducting element is not designed to be level, - and that the flat light-conducting element rises from a base plane spanned by an extension plane (E 1) of the second narrow side and a main radiation direction in the direction of a rear corner region of the light guiding element, said corner region being arranged on a side facing a body end edge, and - that the first narrow side is twisted by a twist angle (φ 1) in the direction of the corner region relative to an extension line (E 3) of the first narrow side and/or the connecting side is twisted by a twist angle (φ 2) in the direction of the corner region relative to an extension line (E 2) or the connecting side.