Diamond films were deposited on 3-inch diameter p-type [100] oriented porous silicon substrates using a microwave plasma disc reactor. Thin porous silicon layers were obtained on silicon wafers by anodization in an H2O/HF/C2H5OH solution. Process parameters were varied to obtain the best quality uniform porous silicon films. Diamond films were deposited on these substrates with and without dry seeding techniques utilizing 4-nm diamond particles. Power and pressure were varied in the range of 2800-3300 W and 50-60 Torr, respectively, while the methane concentration was kept constant at 1% by volume in hydrogen. Diamond was successfully deposited on anodized silicon substrates without dry seeding. However, the films were discontinuous in certain regions even after 20 h of deposition and the deposition rate was low. Dry seeding of the porous silicon surface yielded a high deposition rate and uniform films. Porous silicon was found to reduce the intrinsic stress in the deposited diamond film considerably. Furthermore, film adhesion was also improved with porous silicon.