Making decisions, especially when it affects the wider society, we need scientific tools to process the available data. GIS is one such tool of decision making. Application of GIS in the field of Urban Planning, in order to make the optimal decision, is being attempted in this study. Our accurate decision in planning process leads to the successful completion of our plan, while a small error in our decision leads to the entire failure of the plan. Many urban development plans in Sri Lanka unfortunately meet the end of failure or many are abandoned before completion. This is partially due to the improper identification of the prevailing condition of the land area. For a plan to be successfully implemented in an urban area, where the land use, human processes and physical setting are more complex than in a rural area, a prior identification of the vulnerable and desirable regions is a crucial task. Then only the best decisions can be made to treat the vulnerable areas and to preserve the desirable areas. Hence the objective of this study is to develop a GIS-based technology in the identification of vulnerable and desirable regions in urban areas.