This paper summarises student discussions on the newly developed illustrative descriptors for mediation, the fourth mode of language activities and strategies presented in the Common European Framework of Reference for Languages (CEFR) of the Council of Europe. The discussions were carried out during a seminar on Assessment in Language Teaching and Learning with students in a M.A. programme on Teaching Polish as a Foreign Language at the Jagiellonian University in Krak贸w, Poland, in the academic year 2016/17. The development of illustrative descriptor scales for mediation was carried out by a team lead by Brian North and Enrica Piccardo within the context of a wider project supported by the Language Policy Unit of the Council of Europe in Strasbourg