In the present work, the potential of using foam structures impregnated with phase change materials (PCMs) as heat sinks for cooling of electronic devices has been numerically studied. Different design parameters have been investigated such as foam properties (porosity, pore size, and thermal conductivity), heat sink shape, orientation, and use of internal fins inside the foam-PCM composite. Due to huge difference in thermal properties between the PCM and the solid matrix, two energy equation model has been adopted to solve the energy conservation equations. This model can handle local thermal nonequilibrium condition between the PCM and the solid matrix. The numerical model is based on volume averaging technique, and the finite volume method is used to discretize the heat diffusion equation. The findings show that, for steady heat generation, the shape and orientation of the composite heat sink have significant impact on the system performance. Conversely, in the case of power spike input, use of a PCM with low melting point and high latent heat is more efficient.