Various 2-pyrone derivatives are important intermediates in the synthesis of biologically active compounds. Pd chirally modified by cinchona alkaloids has a potential in the enantioselective hydrogenation of 4-hydroxy-6-methyl-2-pyrone to the corresponding 5,6-dihydropyrone. A study of various parameters (solvent, temperature, pressure, concentration) and catalyst systems (Pd/alumina and Pd/titania, modified by cinchonidine or cinchonine) revealed striking variations of the reaction rate and enantioselectivity with conversion. This transient behavior is interpreted by the effect of competitive adsorption and hydrogenation of the substrate and modifier.