This book constitutes the refereed proceedings of the 18th International Conference on Compiler Construction, CC 2009, held in York, UK, in March 2009 as part of ETAPS 2009, the European Joint Conferences on Theory and Practice of Software. Following a very thorough review process, 18 full research papers were selected from 72 submissions. Topics covered include traditional compiler construction, compiler analyses, runtime systems and tools, programming tools, techniques for specific domains, and the design and implementation of novel language constructs.