In the world, there is an increasing problem regarding impregnated wood wastes, due to severe environmental legislation. Combustion and landfilling are not acceptable solutions for this issue at all. Mycoremediation of impregnated wood wastes, using copper tolerant wood decay fungi, is one of the most promissing solutions. In order to elucidate fungal overgrowth of impregnated wood, two copper tolerant (Antrodia vaillantii and Leucogyrophana pinastri) and two copper sensitive (Poria monticola and Gloeophyllum trabeum) brown rot fungal strains were used. Samples were made from Norway spruce (Picea abies); one of them was impregnated with 5 % CCB solution, the other half was not. According to the EN 113 procedure the specimens were exposed to wood decay fungi. After the exposure they were isolated and fungal overgrowth was estimated via respiration measurements. Influence of time exposure on fungal overgrowth was investigated first, then control wood samples and the impregnated ones were immersed into nutrient solution (glucose and/or corn steep liquor), and afterwards the influence of nutrients on fungal growth was analyzed. The results show that tolerant fungal strains colonize CCB impregnated wood faster than the sensitive ones. By measurments of CO2 and of mass losses it was proved that immersing of the samples in general improve the fungal growth.