Boric acid is very effective biocide in relatively low concentrations. It does not have negative influence on humans and environment. Boron compounds do not react with wood and, therefore, leach from it, unfortunately. Furthermore, there are several reports that boron compounds decrease hygroscopic properties of wood. To improve boron fixation in wood boron compounds were combined with montan wax emulsions of various concentrations. It was presumed that addition of wax would lower moisture content of wood during soaking in water, and during conditioning of wood in humid climate. To elucidate this issue, Norway spruce wood specimens were impregnated with selected wood preservatives, based on montan wax and boric acid emulsions. 2 sets of specimens were prepared, 240 for determination of velocity of water adsorption during immersion in water and during conditioning in humid atmosphere (RH = 80 %). 110 specimens were used to prepare sorption curve through conditioning of impregnated and control specimens at 5 different climates (20 %, 33 %, 65 %, 87 % in 98 %). The results show that treatment with water wax emulsions considerably reduces adsorption of water. Besides improvements of fungicidal properties, the combination of montan wax and boric acid also improves sorption properties of wood.