A method of protecting wood. According to the method, an aqueous dispersion of alkyl ketene dimer is applied onto the surface of the wood. By means of this treatment, the surface becomes hydrophobic and the contact angle of water in the form of drops on the treated wooden surface exceeds 100°. Such drop-shaped water does not penetrate into the treated surface, nor into for instance a crosscut end of sawn timber. Instead, the water disappears from the surfaces by evaporation.