This book comprises a collection of chapters concerning novel research on Human-Computer Interaction. Chapters correspond to high-quality selected papers from Interaccion 2007, the 8th annual conference on Human-Computer Interaction held in Zaragoza, Spain, as part of the II CEDI; the second edition of the Spanish Conference on Informatics, the biggest and most important in Spain. This book is particularly aimed at researchers, advanced HCI students and practitioners. It includes promising works that range from cutting edge paradigms such as Semantic Web Interfaces, Natural Language Processing and Mobile Interaction to new trends and interface-engineering techniques such as User-Centred Design, Usability, Accessibility, Development Methodologies and Emotional User Interfaces. It also provides a specialized learning reference for advanced lectures, involving topics such as Human Factors, Collaborative User Interfaces and Model-based User Interface Design.