Noun-Noun compounds (NN) are a concatenation of two nouns that function as a single unit both morphosyntactically and semantically. Two main challenges that a study of NN compounding faces are (i) identifying the implied semantic relations that hold between the nouns and (ii) explaining why NN compounds are or not productive (i.e. not very frequent) and creative (i.e. impromptu creation) in certain languages. Jackendoff ( 2009, 2016) proposed a model which considers the semantic relation between the head and modifier as established by an external function F(X, Y). Since Spanish NN compounds are not creative, the aim is to demonstrate whether the model can be applied to Spanish, and if so, identify the most productive basic functions. This can help us determine whether the lack of creativity of NN compounds in Spanish is due to a restricted set of productive functions. Our hypothesis is that only those relations that are productive are creative and are able to satisfy the Principle of Generalized Modification ( Snyder 2012, 2016) operating at the syntax-semantics interface. The study also provides a comparison with the semantic relations attested in Spanish N-de-N constructions (i.e. buque de guerra ‘ship of war’ = war ship). Since the latter are very productive and creative, I wonder how well our hypothesis would accommodate to the data. The results indicate that few semantic relations are productive which indicates that only those should be used to interpret novel NN compounds satisfying Generalized Modification. N-de-Ns show a larger amount of functions and although the data falls short to accommodate the hypothesis, impressionistic observations tell us otherwise. Given this asymmetry, our results provide important evidence for blocking effects at the interface: the availability of the NN form blocks the surfacing of the prepositional alternative and viceversa.