Adposition phrases in morphologically impoverished languages have a function similar to nouns with morphological cases in morphologically rich languages, leading some researchers to argue that at least some cases belong to the category P. The aim of this paper is to investigate whether all cases can be analysed as Ps. The focus is on partitive case in Finnish. Whilst the ‘local’ cases in many languages appear to be strong candidates for analysis as members of the category P, it will be argued that partitive case (and genitive in languages where there is no distinct partitive) spells out a functional head between P and D, and that it properly belongs to the D-system (quantifiers or determiners), not the P-system. Thus morphological cases do ...