The origin of the photoluminescence (PL) shifts in Porous Silicon(PS) is discussed according to a quantum confinement – based model, inwhich we modelize the PS layer as a mixture of quantum dots and wires. Itwas shown that a PL blueshift or redshift may occur during laser irradiationof PS, depending on preparation conditions. No PL shift was observed forsome PS samples, even after a long ageing in air, due to the presence of anamorphous silicon phase detected from Raman spectroscopy measurements. Itwas found that the presence of the amorphous phase plays an important rolein the PL behaviour of oxidised PS.