Copper based preservatives are very effective and frequently used fungicides. However, their most important disadvantages are low fixation in wood, usage possibilities of copper impregnated timber, particularly where leaching of active ingredients appears. Fixation of copper can be significantly improved in combination with amines and carboxylic acids. We wanted to elucidate how the initial humidity of wood influenced copper leaching. Therefore, specimens made of Norway spruce were impregnated with 4 different preservatives of 3 various concentrations. Preservative solutions consisted of copper (copper(II)sulphate or copper(II) oxide), ethanolamine and octanoic acid. After a full cell vacuum treatment, retentions of preservative were determined gravimetrically. Specimens were dried at room temperature. Leaching of the specimens was performed according to the modified standard method SIST EN 1250/2. Percentage of leached copper in leachates was determined using atomic absorption spectroscopy. The results show that the increased humidity of specimens positively influences the copper fixation. The lowest copper leaching was determined point at samples having cell walls saturated with water (u = 30 %), and the highest at samples with wood moisture content from 0 to 10 %. The composition of preservatives influenced the leaching of copper to. Copper(II) sulphate based preservatives had a better fixation in wood than copper oxide ones.