This paper presents a method for performing expert-based scenario driven usability evaluation of personalisable and configurable web-based systems, based on an innovative method called DEPTH (DEsign PaTterns & Heuristics criteria). DEPTH focuses on the specificities of web-based system functionality, emphasises usability issues within the specific context of their use (eg e-learning, e-commerce, etc) and adopts the main principles of the scenario-based evaluation techniques. The main idea behind DEPTH is to minimize the preparatory phase of a usability evaluation process, and allow a novice usability expert (ie one who is not necessarily familiar with the specific genre/type of the web-based system under evaluation) to perform the usability evaluation study effectively. Towards this goal, we (re) use expert’s design knowledge captured in design patterns for the specific genre of the system under evaluation. Such use of design patterns, which are also associated with scenarios for expert’s inspection, is one of the innovative aspects of our method. In this paper we will describe an example of DEPTH’s application for evaluating adaptive web-based systems, thus clarifying the main points of the method.