This book constitutes the refereed proceedings of the 6th Language and Technology Conference: Challenges for Computer Science and Linguistics, LTC 2013, held in Poznań, Poland, in December 2013. The 31 revised and in many cases substantially extended papers presented in this volume were carefully reviewed and selected from 103 submissions. The papers selected to this volume belong to various fields of Human Language Technologies and illustrate a large thematic coverage of the LTC conferences. To make the presentation of the papers possibly transparent we have "structured" them into 9 chapters. These are: Speech Processing, Morphology, Parsing Related Issues, Computational Semantics, Digital Language Resources, Ontologies and Wordnets, Written Text and Document Processing, Information and Data Extraction, and Less-Resourced Languages.