Paper describes effect of surface preservation of plywood with silicone-in-water emulsion on its hygroscopic properties. Three spread values were applied: 35, 70, i 105 g/m2. Protected 3-ply plywood were exposed on 100% humid air and damped. Obtained results were presented in comparison to unprotected samples of plywood. Decrease of swelling, shrinking and absorbability of tested plywood exposed on 100% humid air and damped was observed.