Abstract:This thesis studies and develops application procedures of multi-attribute value tree methods and related decision support systems. The objective is to understand the needs of practice for the process support and, through this, to help create user-friendly multi-criteria decision support systems and appropriate ways to use them. The motivation behind this is that the usability of the methods is strongly dependent on the available tools and on their application process. The recent advances on the development of computers and the Internet have also created new opportunities to develop the systems. Consequently, the role of computer support has become very process-oriented instead of only implementing the mathematics of the methods. Specifically, the thesis (i) introduces two new web-based systems, Web-HIPRE and Smart-Swaps, with focus on process support and on adopting the new opportunities of computer support, (ii) reports experiences on the use of these systems in environmental applications to support group decision making processes, and (iii) describes new ways to apply two specific methods, even swaps and preference programming, for various tasks with an aim to improve the practical applicability of these methods.