Recently, as the range of users utilizing open data has expanded from experts to students, and general citizens, the role of open data portals has changed. In the past, portals have neglected to increase data utilization through citizen participation by focusing on the role of simple data repository, but now they tend to focus on understanding, collaboration and sharing values so that users can actively use data. To meet these social trends, open data portals need to seek ways to improve user-centered services that can encourage citizen participation. The purpose of this study is to identify the main functions for citizen participation in open data portals, to analyze the current status of open data portal user services and to suggest ways to improve them. Through the literature research, we investigated the functions provided by portal services for citizen participation, deduced the types of user services, and analyzed open data portal user services. Furthermore, we suggested user-centered public data portal services improvement plans for citizen participation.