The integration of wireless and web-based communication technologies in advanced public transport information systems has led to the provision of passenger information services directly to the users. Most of the existing systems provide alternative travel plans either for urban or for single-mode interurban trips. The objective of this paper is to present an online passenger information system for delivering personalized trip-planning services for interurban multimodal trips, including plans for any constituent urban transfer. The proposed system accommodates the provision of critical real-time travel information (e.g., delay or cancelation of flights) to the user throughout the entire life cycle of an interurban trip. The major features of the system are the following: (a) determination of optimum itineraries in a multimodal public transportation network, (b) online updates of the departure times throughout the entire life cycle of the trip, and (c) dissemination of travel information through several communication channels. The proposed system supports two major trip-planning decisions: (a) itinerary planning for an urban trip through the local public transport network, and (b) combined urban and inter-urban trip planning. The focus of the paper is on the presentation of the design and implementation of the proposed system and its application for supporting trip-planning decisions in Greece. An evaluation of the system has indicated that it is user-friendly, is cost-effective, and meets travelers' requirements.