In this article, we argue that the spell-out condition of the Spanish relative determiner CUYO is structurally related with [+WH] complex relative construction under the basic hypothesis that the [Φ-feature] of the Latin possessive relative determiner CUIUS diverges as to the way of its specification in Spanish and Italian, the [+WH}[+REL(ative] element occupies in the Spec of CP, and the [Φ-feature] of relativized element must be explicitly realized in the morphosyntax. We propose an alternative approach based on the previous studies of Kayne(1994), Cardinaletti(1998), Cinque(1995) about the realization of Spanish relative determiner cuyo, in order to account for several previously unaccounted phenomena. We discuss some consequences potentially relevant for the Italian possessive relative constructions, in the light of the Distributed Morphology(cf. Halle & Marantz(1993), Harley & Noyer(1998)), and subsequent works.