Copper compounds are very effective and frequently used fungicides. Their most important disadvantage is their low fixation in wood, which decreases possibilities of use of copper impregnated timber, particularly in places where leaching of active ingredients occurs. Fixation of copper can be significantly improved with addition of amines and carboxylic acids. To find out how time influences the fixation of copper into spruce-wood samples were impregnated with 3 different preservatives in 3 different concentrations: based on copper, ethanolamine, octanoic acid, quaternary ammonium compound and boron; according to the full cell procedure. Then their retention was gravimetrically determined. After pre-determined periods of conditioning (0, 3, 7, 14, and 28 days), samples were leached according to the standard method SIST ENV 1250/2. The percentage of the leached copper in the leachates was determined with the atomic absorption spectroscopy. The results show that the percentage of the leached copper decreases in the first 14 days of fixation, later the percentage begins to increase again. In the first week copper binds via ethanolamine into wood. But after 2 weeks, depolymerisation of wood polymers caused by ethanolamine becomes more prominent and thus influences leaching.