This book constitutes the refereed proceedings of the Second International Conference on Integration of AI and OR Techniques in Constraint Programming for Combinatorial Optimization Problems, CPAIOR 2005, held in Prague, Czech Republic, in May/June 2005.The 26 revised full papers published together with an invited paper and abstracts of 2 invited talks were carefully reviewed and selected from close to 100 submissions. Methodological and foundational issues from AI , OR, and algorithmics are presented as well as applications to the solution of combinatorial optimization problems in various fields.