Wood preservation based on copper is one of the oldest wood protecting methods. In some parts of Western Europe, lower resistance of poles treated with CCB salts to certain fungi (order Poria) was discovered in the mid nineties of the past century. The main issue of the research was testing if EPR spectroscopy can be used for copper(II) sulfate and copper(I) chloride detection in aquatic solutions, and if changes and absorption of copper can be detected in fungus mycelium and PDA nutrient medium over a period of 10 weeks. EPR spectroscopy was discovered to be a suitable method for copper sulfate detecting in aquatic solutions because copper is in paramagnetic active Cu(II) form. On the other hand, copper chloride is in Cu(I) form, and has no paramagnetic centers. PDA nutrient medium, with added copper sulfate, did not affect copper sulfate paramagnetic characteristics. Suitable concentration of copper sulfate in PDA nutrient medium (1 x 10-3 mol/L) was determined. At this concentration mycelium still successfully overgrows the PDA medium and copper can be detected in both (mycelium and PDA nutrient medium). The result of weekly measurements indicates chemical changes of copper in mycelium, PDA medium close to mycelium and deeper in PDA medium at fungus Poria placenta. It was concluded that copper compounds were deposited and aggregated on hypha cover in mycelium. There were some changes at Trametesversicolor as well. Copper almost could not be detected in the mycelium for the first 6 weeks, then a strong and different signal was detected in the 7th week. Evidently, fungus can change copper's chemical form and absorb it through mycelium into a PDA nutrition medium. Substantial changes of copper in Poria monticola and both isolates of Antrodia vaillantii could not be detected with EPR spectroscopy. It is assumed that those fungi have changed copper into a form that cannot be detected with EPR spectroscopy.