The invention relates to a process for adsorption of polymerization inhibitors from ethylenically unsaturated monomers, in which these inhibitors are placed in contact with an alumina exhibiting a volume of pores of diameter greater than 100 Å of at least 0.20 ml/g, preferably of at least 0.25 ml/g, still more preferably of at least 0.30 ml/g, and a specific surface of at least 30 m2/g, preferably of at least 60 m2/g, still more preferably of at least 80 m2/g.