The central aim of this paper is to study the interaction between the grammaticalization process by which prepositions may develop into prefixes, on the one hand, and French and Dutch word structure, on the other hand. More particularly, it will be investigated whether the degree of grammaticalization of a bound preposition is influenced by the category it introduces (verb, noun, adjective, adverb) and whether this influence is the same in French and Dutch. These theoretical issues are applied to a specific case study : the French preposition entre ‘between’ and its Dutch counterpart tussen used as bound morphemes. In the first part, we show that the prepositions entre and tussen share a wide range of uses. In the second part, an extensive morphological, semantic and comparative analysis is applied to the bound uses of both prepositions. The results of this analysis are discussed in part 3.