Geographic information systems (GIS) and their tools support the process of real estate trading. Of key importance is the ability to visualise information about real estate in the form of maps of average real estate transaction prices. The following study presents a methodology for mapping average real estate transaction prices using GIS. The map development process comprised three main stages. In the first stage, the input data was processed and statistically analysed. Official data came from the Register of Real Estate Prices and Values, and open data from the National Register of Boundaries. The second stage involved the visualization of the data in the form of maps of average apartment prices using the cartographic methods of choropleth maps and diagrams. The commercial tool ArcMap 10.3 and the free Quantum GIS software were used in the design of the maps of average real estate transaction prices, to check the options for using these types of programs. As a result, eight maps were designed presenting the average transaction prices for residential properties in the Warsaw district of Ursynów in 2015. The final stage was the analysis of the designed maps. The influence of the selection of the reference units on the visualization content, and the impact of combining cartographic presentation methods on the complexity of the presentation of real estate information, were also analysed.