In this paper, the syntactic properties of the so-called Quesuismo construction in Spanish (cf. RAE-ASALE (2009)) are thoroughly described and analyzed. The Quesuismo construction shows a non-integrated type of possessive relative <que + su>, also characterized as a resumptive restrictive relative clause (cf. Suñer (1998)). This type is not recommended within prescriptive grammar as the standard use of the Spanish possessive relative is the integrated type cuyo. But in current colloquial Spanish, there remains a wide-spread tendency to use the type <que + su>.
Based on the Head Raising Analysis of Kayne (1994) and De Vries (2006), we will try to show the reasons why the raising of the POSSESSOR and the realization of the prenominal possessive SU are required in the Spanish restrictive possessive relative clause with the non-integrated type of <que + su>.