Salt based chemicals tend to increase in hygroscopicity of wood. This phenomenon is known as one of the disadvantages of these salts in wood preservation in spite of their protective effectiveness against biological agents and fire. 'fhis study was designed to determine the rate of hygroscopicity of both some impregnation chemicals treated and untreated beech wood. Impregnation solutions of boric acid (BA) and borax (BX) were prepared by water and polyethylene glycol (PEG-400). Additionally, some water repellents (WR) such as paraffin wax (P), Styrene (St), methylmethacrylate (MMA) and icocyanate (ICO) were used to decrease the hygroscopicity level of beech wood.