Measurements of transmission and enhanced backscattering from powder beds of alpha-Al2O3 consisting of particles with different average sizes are reported. The values of the mean free path and the absorption length, as inferred from these measurements, are compared and good agreement between the two measurements is found when the internal reflections are properly taken into account. A particle size measurement method is suggested on the basis of the linear dependence found experimentally between the transport mean free path and the mean particle size.