Phrasal units, in particular idioms, constitute a considerable number of structures speakers of a language use. However, this processing is similar to the other elements of the linguistic system because they vary as far as their compositionality, syntactical fixation, transparence, idiomaticity, ambiguity and familiarity are concerned (Corpas Pastor, 1996, 2000; Ruiz Gurillo, 2001). In the context of FONDECYT Project N° 1100600, this paper accounts for the debate over the processing of these units in psycholinguistics (Giora, 1997, 2002). To accomplish this purpose, the main approaches to the subject-non-compositional, compositional, and hybrid theories-are described. From this perspective, a comparison of these theories will be made, considering the research paradigm, the features of the idiom, the role played by the context, and the role of syntactical parsing. This analytic process helps understand that the theories arrive at different conclusions because, even if they converge on the phenomenon they study, neither their objects of research nor their approaches to the phenomenon are the same. Aside from shedding light on the ultimate nature of processing in general, the paper concludes that hybrid theories are more precise to account for how the human mind deals with linguistic phenomena involved in idiomatic aspects.