The use of stiffening ribs for automotive exterior parts such as deck lids and hoods has been studied extensively in the past for panels made from sheet molding compound (SMC). These studies show that the presence of the ribs causes some kind of deformation (rib readout) on the cosmetic side which deprives the parts from having a class A surface. These surface deformations are sometimes in the form of protuberances (“hills”) and sometimes in the form of depressions (“valleys”). A review of the literature confirms that there are a multitude of parameters that can cause the formation of rib readout on the surface of SMC panels. In this paper, and for the first time, the role of each of these parameters in terms of contribution to the formation of hills or valleys on the cosmetic surface is identified and discussed. For instance, the polymerization shrinkage of the resin and the thermal contraction of resin-rich regions are recognized to be the factors that cause valleys on the surface. The compressibility of resin-rich regions and the thermal contraction of glass-rich regions and regions with misaligned fibers, on the other hand, are the parameters that cause the formation of hills on the surface. The role of in-mold coating is also examined and an explanation is given of its contribution to the formation of hills on the surface. The effect of the painting process is also discussed, and it is concluded that cure of the paint at elevated temperatures brings out traces of rib readout even when the surface of the part is sanded smooth prior to paint application. In light of this analysis, a proposed set of characteristics is given for an ideal resin with a low profile agent, the polymerization of which will not contribute to the formation of rib readout.