Internet Protocol Television (IPTV) generically designates a real time distribution service for multimedia contents over an IP network, such as the Internet. There are many advantages of IPTV over current digital or air broadcast TV signals: integration, the use of switched IP, the possibility to build home networks to share multimedia contents over different devices, the easy implementation of video on demand services and the usage of better compression standards. In order to implement this kind of service, it is extremely useful to have a system that can efficiently classify multimedia contents and users and distribute them in a customized way. This paper proposes a novel IPTV service for the distribution of personalized multimedia contents over IP networks based on the concept of content-zapping in contrast to traditional channel-zapping, that is, each system client receives a multimedia streaming that is automatically composed by the system based on the user preferences and the user will only interact by requesting a content change or marking the content as a favorite. The general functionality of the service will be described, as well as the detailed architecture of the IPTV server, the key component of the service infrastructure. The server must maintain a list of media contents residing in other systems and must keep a dynamic classification of the multimedia contents that are stored in its database. This classification is built and gradually refined based on the interactions between the clients and the multimedia contents. The system must also keep a profile of the users and their feedback to the different multimedia contents in order to build and update the users preferences. Special attention is given to the classification model, describing the general ideas that are used to automatically suggest multimedia contents to a specific user (characterized by his complete profile).