The paper summarizes the results of an experimental and numerical study performed on the rear door of a car of large production. It was carried out with a DMC ("dough molding compound") plastic material with short glass fibers. This technology makes strong the link between the production process and the mechanical properties of the component. Such properties really vary according to the fibers orientation, the distance from the injection points and the geometrical complexity of the different regions of the molded component. In some regions the fibers orientation is well defined, in others the orientation can be expressed only in average tendency terms, with a large scatter band. It is natural to think that the material modifies its behavior from region to region, showing marked orthotropic properties or, on the contrary, a compensation isotropic trend. These questions make very difficult the FEM modelling, as the analyses carried out on a particular region of the above mentioned rear door display. The numerical results show that merits and defects are present both in the orthotropic and in the isotropic models.