This book constitutes the thoroughly refereed post-conferenceproceedings of the 18th International Conference on Applications ofDeclarative Programming and Knowledge Management, INAP 2009, held inÉvora, Portugal, in November 2009.The 12 revised full papers presented together with 2 invited talks werecarefully reviewed and selected during two rounds of reviewing andimprovement. The conference comprehensively covers the impactof programmable logic solvers in the internet society, its underlyingtechnologies, and leading edge applications in industry, commerce,government, and societal services. The topics of the selected papersconcentrate on three currently important fields: foundations andextensions of logic programming, databases and query languages,declarative programming with logic languages, and applications thereof.