In Europe, most data relevant to energy storage exists in a fragmented form. The major work in the ESTMAP project therefore consisted of compiling existing data in a unified database and exploiting it to optimize energy systems planning. Geologists, engineers and system modellers joined forces to define the format and the content of a database of both subsurface (i.e. in sedimentary basins) and above surface storage sites (existing, planned and potential). The idea is to ensure that the newly compiled dataset will fit the needs for robust modelling, planning and designing on a coherent basis and comparable among Member States and other European neighbouring countries. One of the project output consisted of a geographical database providing information on distribution and expected capacity of existing and future energy storage sites in Europe. Both subsurface storage options (hydrogen, compressed air, natural gas, underground pumped hydro, etc.) and above ground storages (pumped hydro, LNG, liquid air, etc.) were taken into account.In this project, BRGM, assisted by TNO, CGS and VITO, was in charge of data collection for underground energy storage (mainly in sedimentary basins), in order to gather readily available and public data on existing and future potential storage sites. These data incorporate the geographic location, geological description and characterization, subsurface properties, and feasibility and capacity assessments of the subsurface reservoirs (aquifers, salt formations and caverns, depleted hydrocarbon reservoirs…).A co-operation with European national geological institutions has been established; the ESTMAP geological subsurface database populates data from EU member countries, the countries of the European Free Trade Association-EFTA (4 countries) and the Member of the Energy Community (8 countries). About 1000 subsurface sites spread around Europe have been identified during the subsurface data collection. All of them have assessment information per technology, in term of proven, likely, possible, unknown, or unlikely feasibility of energy storage.All these data were forwarded for integration in the database to compute further pan-European and regional energy system analyses. The ESTMAP project provided the opportunity to review the available public geological subsurface data in the European countries. These encouraging results let open the possibility for further European cooperation in the future.