In recent years, several studies have suggested that Null Subject Languages (NSLs) do not exhibit uniform behaviour in all respects. This paper aims to determine whether the interpretation of null and overt subject pronouns in Spanish differs from that in two other NSLs: Italian and Greek. To this end, we replicated the sentence interpretation experiment conducted by Torregrossa et al. (2020) on Greek and Italian to obtain a fully comparable set of data.The results indicate that Spanish differs significantly from both Italian and Greek in the interpretation of null and overt pronouns. Spanish participants accept null subjects referring to both subject and object antecedents to the same extent. The same pattern is observed for overt subject pronouns. To explain the observed differences, we propose that two properties of its grammar influence the interpretation of null subjects and overt pronouns in Spanish: i) a flexible word order, allowing for SVO, VSO, and VOS; and ii) the existence of differential object marking (DOM). We hypothesise that these two factors may affect antecedent selection, thereby partially accounting for the differences observed among the languages under consideration.