Cross-border geological mapping is essential for proper understanding of the Poland’s border areas geological setting and their mineral potential. Close co-operation with geological institutions of the neighbouring countries is, therefore, necessary. The joint detailed geological mapping of the cross-border areas was difficult until 1990 because of security reasons. The whole Polish Geological Institute’s mapping activity concentrated, until that time, on very general cartographic presentations of the regional, European or world-wide geology, tectonics, palaeogeography, mineral perspectives, and so on, in the adequately small scales. Since the early 1990s the Institute started to develop more systematic, geophysical, geological and geo-environmental mapping of the common cross-border areas with the national geological surveys and other geological institutions of the neighbouring countries. The most systematic and most detailed cartographic surveys have been carried out so far with the German geological surveys. The Czech, Slovak, and Lithuanian surveys cooperated also very actively. A great cartographic effort has been made on the Baltic Sea geology, as well. Geological mapping co-operation with the Ukrainian, Belarusian, and Russian institution is eventually slowly building up, too. This paper presents the up-to-date results of the joint Polish Geological Institute and the neighbouring geological surveys activities in the geological mapping of the cross-border areas, as well as some current, mapping related activities.