The study was aimed at testing environmental-friendly plant essential oils for their protecting efficiency of valuable woods against colonization by mould and wood-decay fungi. Sixteen essential oils were applied to Fagus orientalis and Pinus taeda wood samples by vacuum impregnation and infected with Aspergillus niger, Penicillium commune (moulds), Coniophora puteana (brown rot), Trametes versicolor (white rot), Chaetomium globosum (soft rot) and natural infection by airborne spores. Lavender oil, lemon grass oil and thyme oil were the most effective oils against all fungi tested.