The comparative inhibition of the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2amino-3,8-dimethyl-3H-imidazo[4,5-f]quinoxaline (MeIQx) by phenolics in both model systems and beef patties was studied to better understand the protective role of these compounds. Model systems were selected to produce PhIP and MeIQx by carbonyl-amine reactions. Obtained results showed that their formation was inhibited up to 100 % by assayed phenolics. Among simple phenolics, m-diphenols were usually more effective than o-diphenols, and MeIQx was better inhibited than PhIP because m-diphenols both produce the Strecker degradation of amino acids to a lower extent than o-diphenols, and trap acrolein (responsible for MeIQx formation) better than phenylacetaldehyde (responsible for PhIP formation). When complex phenolics were assayed, other groups also contributed to the observed protective function. However, relative inhibitions of both compounds in model systems and beef patties were correlated, therefore suggesting that the formation of PhIP and MeIQx also occurs in beef patties by carbonyl-amine reactions.