This book constitutes the thoroughly refereed post-conference proceedings of the 4th IFIP TC2 Central and East European Conference on Software Engineering Techniques, CEE-SET 2009, held in Krakow, Poland, in October 2009. The 19 revised full papers presented were carefully reviewed and selected from 63 submissions. The papers are organized in topical sections on software architectures and development; modelling and formal methods in software development; measurements, testing, and quality of software.