One of key problems that users meet when interacting with any software product is easiness of communication with such a product - we speak about usability issues. This problem has not been addressed properly in case of software products used in ICT assisted learning. In this paper we will deal with usability issues in this field. There are various systems that support ICT supported learning like e-learning, m-learning, t-learning etc. We will present experience with usability testing in t-learning (iDTV - Interactive Digital Television) environment. The topic that was taught in the iDTV learning module was cultural heritage. This topic offers a possibility to use various media (text, pictures, videos etc.) together with different ways of interaction. In such a way the requirements for usability in this environment are rather complex. The paper describes the usability issues handled in individual stages of the learning module development ...