This paper discusses why Spanish possessive pronouns cannot license nominal ellipsis, contrary to other determiners such as definite articles, demonstratives and numerals. In previous literature, there have been some attempts to elucidate the incompatibility of possessive pronouns with nominal ellipsis, assuming that possessive pronouns are determiners just like definite articles, demonstratives or numerals, all of which are located in the head position of the DP. However, in this paper I argue that the incompatibility between possessive pronouns and nominal ellipsis is due to the fact that the former is not located in D and hence cannot allow the latter under the Head-Comp configuration. To support this claim, I first review previous analyses on possessive pronouns involved in nominal ellipsis, and then I propose an alternative in which the possessive pronoun occupies the specifier of DP and hence it is not in a structural position eligible to license nominal ellipsis. In this way, the incompatibility of possessive pronouns with nominal ellipsis can be explained in a more principled way.