The design of eHealth systems calls for a clear needs analysis and functions based on the users’ perspective. However, this is often the most difficult part of designing eHealth service systems, because of the diversity of users and diversified needs. This paper provides a general mapping and overview of the basic functions of eHealth systems identified through two studies: (1) a comprehensive study of the resource book of eHealth projects under the European Sixth Framework programme (FP6), and (2) a theoretical study based on the framework of Activity Theory. The first study provides the eHealth system designers with an overview of a number of important and particular functions that the users/citizens need in order to get good services; while the second study presents a fundamental ‘skeleton’ and architecture for providing those particular functions in an orderly and coherent system.