There are many tools to manage spatial data. They called Geographic Information System (GIS), which apart from data visualization in space, let users make various spatial analysis. Thanks to them, it is possible to obtain more, essential information for real estate market analysis. Many scientific research present GIS exploitation to future mass valuation, because it is necessary to use advanced tools to manage such a huge real estates' data sets gathered for mass valuation needs. In practice, appraisers use rarely these tools for single valuation, because there are not many available GIS tools to support real estate valuation. The paper presents the functionality of geoinformatic subsystem, that is used to support real estate market analysis and real estate valuation. There are showed a detailed description of the process relied to attributes' inputting into the database and the attributes' values calculation based on the proposed definition of attributes' scales. This work presents also the algorithm of similar properties selection that was implemented within the described subsystem. The main stage of this algorithm is the calculation of the price creative indicator for each real estate, using their attributes' values. The set of properties, chosen in this way, are visualized on the map. The geoinformatic subsystem is used for the un-built real estates and living premises. Geographic Information System software was used to worked out this project. The basic functionality of gvSIG software (open source software) was extended and some extra functions were added to support real estate market analysis.