It is often assumed that idiomatic constructions basically involve non-compositional meanings (Katz and Postal 1963; Fraser 1970; Chomsky 1980, among others) or special syntax-semantics correspondences (cf. Jackendoff 1990, 1997a, b, 2002). However, we agree with those linguists who claim that there are aspects of idioms that are compositional (Marantz 1996, 1997; Nunberg, Sag, and Wasow 1994). In this article, on the one hand, assuming Hale and Keyser's (2002) configurational theory of argument structure, we show that a class of idiomatic constructions which can be found in both "satellite-framed languages" like English and "verb-framed languages" like Catalan and Spanish (Talmy 1985, 1991, 2000) involves different applications of a lexical syntactic process of conflation. Unlike Jackendoff (1990, 1997a), we argue that the relevant crosslinguistic variation must be expressed in l(exical)-syntactic terms rather than via correspondence rules. On the other hand, assuming Marantz's (1996, 1997) division of labor between the computational system and the encyclopedia, we show the relevance of syntactic argument structures in structuring the compositional meaning of an idiomatic construction, and that of distinguishing between syntactically transparent compositional meanings and syntactically non-transparent non-compositional ones. © Walter de Gruyter 2007.