The main topic of this thesis are the multiword expressions in the italian language. The thesis is divided into two parts - the theorical and the empirical part. The theorical part deals with the multiword expressions, the syntagmas and the idiomatic expressions. In the empirical part the connections between the constituents of the multiword expressions will be researched. Than four criteria will be on the multiword expressions applied (head inflection, insertion of the head's modifiers, pronominalisation of the head and dislocation and topicalization of the head). These transformations will be verified with the aid of corpora and questionnaires. Depending on the results of this research will be decided if the multiword expressions resemble the syntagmas or the idiomatic expressions.