One of the most intriguing properties of pronominal clitic clusters is that some clitic combinations, although logically possible, are unattested. This dissertation proposes a syntactic analysis in the cartographic tradition of the co-occurrence restrictions of pronominal object clitics in Romance, with an emphasis on Romanian. It is proposed that the cliticization patterns of Romanian clitics are derived by a structural implementation of person and case hierarchies, in conjunction with locality constraints on clitic movement. It is furthermore shown that Romanian singular and plural clitics exhibit different behavior. I argue that this is the result of (defective) intervention effects due to case syncretism on clitics, which interact with (remnant) VP movement.

The system devised for Romanian is further developed to account for several clitic combinations in Western Romance. I propose that the locus of parametric variation lies in (i) the way in which Person features are encoded in the Person field and (ii) the availability of case syncretism (or lack thereof) with clitics. Within the cartographic project, my analysis provides independent evidence from cliticization patterns in Romance that the strong hypothesis regarding the universality of the order of functional projections cannot be upheld (at least not entirely). From a larger perspective, this research on clitic combinations suggests the possibility of further elaborating my analysis in order to account for superiority effects in languages with multiple wh-fronting.