The goal of this research was to develop a model of architecture for a virtual one-stop public administration. The first part of our work was to collect data during a six-month survey in a Swiss cantonal administration and to conduct an online survey of Internet users in order to discover their expectations. Using this data we identified and classified the different relations or interactions that a public administration can have with its clients. Then we categorized the different functions and departments of an administration, as well as the different types of clients. After having defined this typology we built a model of a one-stop public administration, studying both the structural and the behavioural aspects of such a system. Finally we proposed a component-based architecture for building this system on the Internet, showing how it relates to the conceptual model and why this architecture suits our needs best.