The development of technology, coupled with the economic and the environmental changes, fostered interest in "smart cities" concept, that is cities where "investments in human and social capital linked with traditional and modern communication infrastructure fuel sustainable economic growth and a high quality of life, with a wise management of natural resources, through participatory governance". In this direction, the city of Bergamo is approaching the smart city paradigm proposing new services and innovative solutions aiming at reducing costs and resource consumption, and at shortening the distance between citizens and city government. During a project with the University of Bergamo, many possible solutions to comply with this paradigm were highlighted. Budget constraints spurred to compare the ideas, and to select the most valuable to be implemented first. In order to facilitate the ranking and the prioritization of the ideas, a two-step assessment method based on Importance Performance Analysis (IPA) developed in the area of Product-Service System was applied in this study. The method, based on Multi Criteria Decision Making mechanism, is composed of two different steps, focusing on two different levels of detail, and it proposes specific evaluation criteria for the providers (i.e. The municipality) and for the customers (i.e. The citizen). The contribution of this study is twofold: first, it complements the IPA-based multi criteria decision-making method with the definition of specific evaluation criteria for external stakeholder that play a crucial role into the smart city paradigm; second, it describes the application of the method for the selection and prioritization of smart city alternatives in Bergamo context.