Copper-ethanolamine based preservatives are one of the most important preservatives for wood protection in 3rd and 4th use class according to EN 335-1/2. They are often used to protect spruce wood, naturally not durable enough, nevertheless, frequently used for construction applications. One of the issues related to copper-ethanolamine solutions is insufficient penetration, and copper leaching from impregnated spruce wood. In order to overcome these issues, commercial Cu-EA based solution was supplemented with five different wood swelling agents (ammonia, dimethyl sulfoxide, ethylene glycol, triethanolamine and formic acid) in three different concentrations (2.5 %, 5 % and 10 %). Spruce wood specimens were impregnated with particular solutions, and two different protocols were utilized (vacuum and vacuum-pressure). Uptakes of preservative solution, depth of penetration and percentage of leached copper were determined according to ENV 1250-2. The results show that formic acid and triethanolamine improve the depth of penetration and uptakes of preservative solution, but on the other hand, both of these wood swelling agents increase copper leaching from impregnated wood.