We discuss the role of LO-phonons confinement in quantum well systems, by comparing two different phonon models that have been proposed in the literature. A critical discussion concerning the use of macroscopic approaches for the description of phonons in two dimensional systems is presented. We use a Monte Carlo simulation which includes nonequilibrium phonon effects as well as carrier-carrier scattering to determine the effect of phonon confinent on the relaxation of photoexcited carriers in A1GaAs-GaAs quantum wells. Good agreement with available experimental data is found. Even at low excitation densities, intercarrier scattering and phonon reabsorption are important, and need to be taken into account in the interpretation of experimental data.