The relative preference for a target product over a competitor can be increased by providing a third alternative (a decoy) that is clearly inferior to the target but is not necessarily inferior to the competitor. We investigated how these “decoy” effects are influenced by the presence or absence of brand name information and the level of consumer brand knowledge. A field experiment was conducted with three hundred and twenty married females. Results indicated that overall, inclusion of a decoy in the choice set significantly increased the relative preference for the target (i.e., a decoy effect). However, identifying alternatives with real brand names eliminated this effect when participants possessed an extensive amount of knowledge about the brands, but it did not when participants had relatively limited knowledge. These results were generally consistent with implications of the category-based processing view about brand name information.