The effects of pore structure evolution on the predictions of chemical vapor infiltration models are investigated in this study. A general multicomponent reaction and transport model is used to describe transport and reaction in the pore space, and structure evolution is modeled by representing the void space by a population of cylindrical capillaries (capillary models) or of the solid phase by a population of solid cylinders (fiber models). The capillaries are assumed to be randomly arranged in space without preferred orientation, whereas the fibers are taken to be parallel to a line, parallel to a plane, or without preferred orientation (one- two- or three-directional structures, respectively). The obtained results show that the way in which the pore structure evolves during densification plays a dramatic role in determining the overall behavior of the deposition system. In the case of the fiber structures, the results are influenced significantly not only by the directionality but by the direction of diffusion relative to the fiber axes as well.