The use of filler for the manufacture of paper and board products the air permeability of which does not substantially change as a function of the amount of filler, the filler being at least in part made up of cellulose or lignocellulose fibrils on which there have been deposited light-scattering material particles the proportion of which is 67-85%, preferably approx. 70-82%, of the weight of the filler.