Reengineering of retail networks is a continual process that has been in the forefront of management attention worldwide. The central question is how to achieve positive business results under high costs, but at the same time maintain the attained service quality. This reeingieering process may be implemented successfully only if preceded by detailed preparations concerning, primarily, the analysis of business results, market potentials and retail outlet location. GIS tools offer a strong support to this process. Apart from theoretical considerations, this paper will also present the use of GIS as a tool in determining the optimal locations of the Serbian post retail.