Compet-Terra is carrying out QA (Quality Assurance) services for the Hungarian Agriculture and Regional Development Agency. Quality control of the LPIS is one of the important QA duties. The LPIS data set is updated yearly according to the cycles of agricultural subsidies. Compet-Terra elaborated an Open Source Software based checking method that could be adopted by the client without the financial expense of software.QuantumGIS (as the primary tool), gvSIG, and LibreOffice were used for the quality control of the LPIS. Four primary quality types were checked: (1) the land parcel attributes, (2) the areas of the polygons, (3) the completeness of the content and (4) the topological quality. For these investigations topological GIS functions and database management functions were used. The most important functions were topological difference calculation, polygon area calculation and geometry validity check. Complex procedures were also carried out with proprietary tools to compare the results and the run-time performances.The result of the adoption of OSS GIS tools for LPIS checking was positive. All the planned procedures could be implemented using OSS GIS. OSS tools proved to be robust, reliable, userfriendly and performed well.