jats:pThe present research aims to investigate the interface phenomenon of third-person subject distribution in two prototypical null subject (NS) languages, Greek and Spanish focusing on Chilean Spanish, in adult monolingual speakers. The data were obtained from oral production of narratives (Study 1) and anaphora resolution (AR) (Study 2). All elicited data were submitted to statistical analyses while the production data were as well qualitatively scrutinised. Greek and Spanish were directly compared in order to discover differences between them, which were expected to emerge in the scope of the overt subject pronoun (OSP). The two languages were largely similar, sharing analogous clause structures and displaying generally similar properties on the distribution of subject forms, i.e. NS, OSP, as well as lexical subjects (LS) in oral production. The findings, confirming the predictions, showed crosslinguistic differences in the scope of OSP in topic shift (TS) between the languages due to deictic distinctions, with Greek OSP carrying deictic properties, which are less pronounced in its Spanish counterpart. This evidences the fact that NS languages may not be identical regarding subject distribution. Another key aspect, which emerged in the oral production data in both Greek and Spanish, was the felicitous use of NS in TS contexts. NS were also found to be flexible or ambiguous in AR in both languages, thereby displaying a more variable distribution than sometimes assumed.</jats:p>