Particularly in the last decade, there have been a number of efforts to develop and then integrate planning support systems into existing geographic information systems. This integration brought a new technology called WebGIS, which enables geographic information systems functionalities through the Internet for decision support. No doubt there is a growing demand as more and more individuals want to use online government services to express their views and most importantly to take part in decisionmaking processes interactively. At this point, WebGIS offers a challenging opportunity for online participatory planning since the public could easily access alternative plans and the existing information in geographic information systems databases. This technology enables individuals to be able to take part in plan-making processes and contribute. This chapter explores how these new technological advances could achieve truly transparent plan-making process based on online participatory planning support tools that knowledge-based urban development could benefit from.