In the present paper we support that a sub-group of discourse particles may function both as signals related to the structure of the discourse and as indicators of positive politeness, which is characteristic of Modern Greek (Sifianou 2001). Thus, this subgroup of discourse particles, which we will name “politeness markers” demonstrates a double function, since it also constitutes a cultural element in Modern Greek dialogs. In contrast to the “politeness markers”, we additionally observe that another subgroup of discourse particles, referred to as “non-politeness markers”, function as signals indicating lack of positive politeness and pleasant attitude in Modern Greek dialogs. The behavior of discourse particles was evaluated for the construction of a dialog system for Speech Technology applications in the domain of customer service, namely the tourist industry. Specifically, the proposed double function of the “politeness markers” in Modern Greek is supported by two types of corpora, a corpus of Greek dialogs built for the tourist industry as well as an additional corpus of spoken Greek journalistic texts. The latter corpus served as a primary resource for the incorporation of discourse and other linguistic elements in the constructed corpus of Greek dialogs.