This paper presents a corpus-based study on the co-occurrence of lexical modal markers expressing possibility or necessity in the six comedies written by Terence. Although the co-occurrence of modal markers has long been discussed in the literature, a systematic and comprehensive study of this phenomenon is still lacking, and studies on Latin are almost absent. In this paper I will first provide a quantitative overview of the phenomenon, discussing my methodological approach and challenges linked to it. Then I will delve into the qualitative analysis of the passages with co-occurrence, focusing on both the interactions observed between types of modality and the use of the co-occurrence for argumentative purposes in specific contexts.