The first worldwide overview of Planning Support Systems (PSS) and their application in practice. PSS are geo-technology related instruments consisting of theories, information, methods, tools, et cetera for support of unique professional public or private planning tasks at any spatial scale. The aim is to advance progress in the development of PSS, which are far from being effectively integrated into the planning practice. The text provides an Internet-based worldwide inventory of innovative examples and successful applications of PSS in a number of different planning contexts. In-depth insights into the purposes, content, workings, and applications of a very wide diversity of PSS are given.