The present invention relates to a method for the hydroxylation of phenols and phenol ethers by means of hydrogen peroxide. The invention specifically relates to a method for the hydroxylation of phenol by means of the hydrogen peroxide. The method of the invention for the hydroxylation of a phenol or phenol ether by means of reacting said phenol or phenol ether with the hydrogen peroxide in the presence of an acid catalyst is characterized in that it includes mixing a phenol or phenol ether with a hydrogen peroxide solution in a mixing device under conditions enabling the conversion rate of the hydrogen peroxide to be minimized, and in that said reaction mixture is then placed in a piston flow reactor where the reaction leading to the production of the hydroxylated material takes place, the acid catalyst being fed into the mixing device and/or into the piston flow reactor.