The prenominal position X and the postnominal position Y within a DP [DPXNY], where N is the head noun, are asymmetric in various respects. Most typically a given category can appear in a given language in one position but not in the other, or can appear only in one or the other under specific regular conditions. In other cases prenominal and postnominal positions give different semantic interpretations of the same element. Allomorphic choice is also affected by position. In this paper we examine some specific cases of Catalan and Spanish in which an asymmetry between prenominal and postnominal elements within the DP arises with respect to inflectional endings. We argue that this kind of asymmetry, present in other languages, is due to postnominal concord taking place in the syntax systematically and prenominal concord being established through constraint evaluation at PF.