Structural foams (SF) have received an increasing attention mainly because of their specific mechanical properties (strength to weight ratio) as well as lower in-mold residual stresses. Injection molding of SF is one of the most suitable approaches to produce parts having a foamed core sandwiched between two un-foamed skins. Predicting elastic properties from the foam structure or even better from the processing parameters is critical to optimize the performance of the plastics parts. Therefore, this study focuses on the prediction of the tensile, shear and flexural moduli of polypropylene structural foams prepared by injection molding under various processing conditions, especially as far as thickness is concerned. Injection molded SF were machined to remove the skins and to recover the core only. The tensile and shear moduli of each layer were measured and compared to the predictive models. Measurements of tensile, shear and flexural data were also performed for the overall SF and compared to predictions of models for cellular materials and polymer composites. For the tensile and flexural data, classical models of the literature were used, while for the shear modulus, a new model was proposed, taking into account the amplification of shear strain due to the negligible effect of the sandwich skins. The models were found to be predictive and they provide a reliable tool for a fine tuning of the process parameters to obtain the desired properties.