This is the refereed proceedings of the 9th International Symposium on Component-Based Software Engineering, CBSE 2006, held in Västerås, Sweden in June/July 2006. The 22 revised full papers and 9 revised short papers presented cover issues concerned with the development of software-intensive systems from reusable parts, the development of reusable parts, and system maintenance and improvement by means of component replacement and customization.