The 5th International Conference on Integration of AI and OR Techniques in Constraint Programming for Combinatorial Optimization Problems (CPAIOR 2008) was held in Paris, France May 20-23, 2008. The purpose of this conference series is to bring together researchers in the ?elds of constraint programming, arti?cial intelligence, and operations research to explore ways of solving large-scale, practical optimization problems through integration and hybridization of the ?elds' di?erent techniques. Through the years, this research community is discovering that the ?elds have much in c- mon, and there has been tremendous richness in the resulting cross-fertilization of ?elds. This year, we allowed submissions of both long (15 page) and short (5 page) papers, with short papers either being original work, a reduced version of a long paper, or an extended abstract of work published elsewhere. We were not s- prised by the 69 submissions in the long paper category: this is an active ?eld with many researchers. We were surprised by the 61 short paper submissions. This was far more than predicted. With 130 high-quality submissions, compe- tion for acceptance in this year's program was particularly ?erce. In the end, we accepted 18 long papers and 22 short papers for presentation and publication in this volume.