The paper presents a study on the effect of water activity and raw material composition on flowability of infant milk powder. Investigated material was diversified in terms of lactose content (21-57.8%). Analysed mixtures were wetted to the water activity of 0.1; 0.2, 0.5 and 0.9. Water content and activity, mean size of particles, loose and tapped bulk density, Hausner ratio and Carr index, pouring time, angle of repose, angle of slide on a stainless steel and glass wall were measured as physical properties. On the basis of studied material a significant effect of water activity and raw material composition on the flowability of infant milk powder was found. Tested modified milk powders were diversified on particle size distribution, bulk density and flowability. Wetting the material to water activity 0.2 (agglomeration), 0.5 and 0.9 caused improved flowability, increased particle size and decreased bulk density of modified milk powders.