This study explores the processing of noun-prep-noun combinations in prepositional phrases in Brazilian Portuguese, focusing on the syntactic-semantic relationship marked by prepositions, implies the semantic sense in which the noun is being modified. We chose to contrast particularly two types of thematic relationships like 'made of' and 'made for’, categorized as: material and function (e.g. ‘toalha de crochê’, crocheted cloth vs. agulha de crochê, crochet needle). To do so, we conducted two psycholinguistic experiments: Experiment 1 consisted of a self-paced reading/picture matching task to investigate the impact of semantic relationship on processing time; and Experiment 2 employed a cloze task (e.g. ‘toalha de ______’) and Likert scale likelihood judgments to norm the stimuli and assess cognitive preferences for the types of relation explored (i.e., material or function). Our results revealed slower reading times for the function type relation, suggesting a higher processing demand, possibly due to covert semantic computations required for this relation. Cloze completions and likelihood ratings also indicated a cognitive preference for this type of relationship. We attribute these observed patterns to the robust syntactic-semantic relationship inherent to functional type relations, coupled with a broader range of potential response options. In contrast, material type relations demonstrated a higher level of convergence among participants for cloze responses, likely due to more restricted response options and, consequently, increased probability. Future EEG studies are proposed to identify specific moments in the cognitive processing of the constituents of these structures and assess possible anticipatory effects of prepositional phrase modifiers. These discoveries make a meaningful contribution to the broader literature on language processing, aligning with analogous patterns observed in different languages with a cognitive distinction between thematic relations and feature-based (i.e., telic and constitutive relations), such as in Wisniewsky & Love, 1998; Estes et al., 2003, 2011; Pustejovsky et al., 2016; Flick et al., 2021.