The paper shows the differences between Greek native speakers and advanced learners of Greek as a foreign language in responding to thanks. More specific, it examines the differences in the production of head acts and supportive moves realizing thanks responses in situations that differ in the object of gratitude and the social relationship between the interactants. The data comes from discourse completion test and verbal reports. Thus, the study provides empirically based information over the difficulties that learners may face when producing such common speech acts in L2. Concluding, the author adds certain implications for L2 acquisition and teaching.