The 9th East-European Conference on Advances in Databases and Information Systems was held on September 12–15, 2005, in Tallinn, Estonia. It was organized in a cooperation between the Institute of Cybernetics at Tallinn University of Technology, the Department of Computer Engineering of Tallinn University of Technology, and the Moscow chapter of ACM SIGMOD. The main objective of the ADBIS series of conferences is to provide a - rum for the disseminationof excellent researchaccomplishmentsand to promote interaction and collaboration between the Database and Information Systems research communities from Central and East European countries and the rest of the world. The ADBIS conferences provide an international platform for the presentationofresearchondatabasetheory,thedevelopmentofadvancedDBMS technologies, and their advanced applications in particular in information s- tems. The 2005 conference continued the ADBIS conferences held in St. Pete- burg (1997), Poznan (1998), Maribor (1999), Prague (2000), Vilnius (2001), Bratislava (2002), Dresden (2003), and Budapest (2004). The conference c- sisted of regular sessions with technical contributions reviewed and selected by an international Program Committee, as well as of invited talks and tutorials given by leading scientists. For the ?rst time the ADBIS conferences had a satellite event, a workshop on data mining and knowledge discovery. The ADMKD 2005 workshop,with its own international ProgramCommittee as well as proceedings, servedas a forum toencourageresearchersandpractitionerstodiscussandinvestigatedatamining research and implementation issues, and to share experience in developing and deploying data mining systems.