To elucidate sorption properties of preserved wood, Norway spruce wood specimens were prepared. One half of the specimens was treated with copper(II)sulphate and ethanolamine based wood preservatives (CuS, CuSEA, CuSEAQBOK) of 2 different concentrations, and the other modified at 180 °C, 195 °C, 210 °C, 225 °C, 240 °C. All the specimens were exposed in chambers with different air humidity (33 %, 44 %, 65 %, 88 %, 98-100 %). Afterwards, adsorption and desorption curves were calculated. Results indicate that besides copper(II) sulphate and ethanolamine other components of preservative solution like boron, quaternary ammonium compound and octanoic acid, have influence on increased hygroscopic properties of impregnated wood. On the other, all thermally modified specimens exhibited lower equilibrium moisture in comparison to control unmodified wood. There is a significant correlation between sorption properties and mass losses caused by thermal treatment. Higher temperatures of modification result in higher mass losses, what is reflected in lower equilibrium moisture content and hygroscopic properties.