This book contains the thoroughly refereed and revised best papers from the 5th International Conference on Web Information Systems and Technologies, WEBIST 2009, held in Lisbon, Portugal, in March 2009, organized by the Institute for Systems and Technologies of Information, Control and Communication (INSTICC), in collaboration with ACM SIGMIS and co-sponsored by the Workflow Management Coalition (WFMC).The 22 papers presented in this book were carefully reviewed and selected from 203 submissions. The papers are grouped in four parts on Internet Technology; Web Interfaces and Applications; Society, e-Business, and e-Government; and Web Intelligence.