The invention relates to a method for illuminating an interior equipment part or an interior trim part (4) in the interior of a motor vehicle, in which at least one elongate optical waveguide (5) is arranged on the interior equipment part or interior trim part (4) and light beams (L) of at least one lamp (3) are coupled into at least one light input point (5a, 5c) of the at least one optical waveguide (5) and are coupled out again from at least one light output point. According to the invention, the diffusion of the coupled-in light beams (L) in the longitudinal extent (LE) of the optical waveguide (5) is interrupted at least at one point (S1, S2) of the optical waveguide, wherein the light at this point (S1, S2) is interrupted at least in such a part of the optical waveguide cross-sectionwhich has a surface that can be freely viewed by a vehicle occupant. A method of this kind makes it possible to illuminate interior equipment parts or interior trim parts in the interior of the motorvehicle in a pleasant and homogeneous manner. The invention further relates to a drinking vessel holder and an interior trim part for carrying out the method.