Introduction.

Recent research on the nature of structural configurations has shown that the complementizer system is to be conceived of as a structural zone consisting of distinct functional heads and their projections, much as the IP system and the DP system. The analysis proposed in Rizzi(1997) postulates a fixed component, involving the heads specifying Force and Finiteness, and an accessory component involving the heads of Topic and Focus, which are activated when  needed, i.e. when there is a topic or focus constituent to be accommodated in the left periphery of the clause. In this paper, I would like to investigate more closely the position occupied by the interrogative complementizer se (“if”) occurring in embedded questions in Italian, and show that it occupies a position distinct from and lower than the position of the declarative complementizer che (“that”). I will then suggest that the projection headed by such an interrogative head is presumably one that may host the Wh element perché (“why”) and other sentence adverbials in main and embedded interrogative clauses, an assumption which helps explain certain peculiarities of such elements in Italian and other Romance languages.