The main objective of the Image Indexing by Content network (I2Cnet) is to provide network-transparent content-based access to medical image archives based on a collection of interoperable Internet/intranet added-value services. This paper discusses I2Cnet, focusing on its service architecture paradigm. I2Cnet services such as image annotation, processing, description, and content-based retrieval, as well as the on-line collaboration service are presented. Exemplary user sessions are used to illustrate how virtual workspaces facilitate the interoperation of I2Cnet services, following the "network computer" approach to information management.