Abstract: The paper presents the authors' experience in designing and implementing secure smart card and agent-based telecommunication services supporting user mobility and service personalization. The work described here has been performed as part of the EU ACTS SCARAB project and is based on a service architecture that has been defined by the SCARAB partners. User mobility is achieved both by using smart cards and by supporting mobile terminals based on a 3Com Palm computer connected to a GSM phone, in addition to fixed PC-based terminals. An on-line travel agency service, that can be used to buy travel tickets, has been implemented as a case study. This paper focuses mainly on the description of the SCARAB service architecture and of the on-line travel agency demonstrative service and on its implementation for the mobile terminal, which is the most critical one, because of the severe resource limitations of Palm computers.