The diffusion of photoexcited carriers in porous silicon strongly affects their recombination dynamics. This is evidenced by a detailed study of the room temperature time-resolved photoluminescence of porous silicon samples with various porosities. Monte Carlo simulations of the photoexcited carrier diffusion by the trap-controlled hopping mechanism in a disordered array of silicon quantum dots have been performed to elucidate the interplay between on-site recombinations and diffusion of carriers. The numerical results are in good qualitative agreement with the experimental data.