The invention relates to a method for improving the quality of service for data traffic in a mobile communication system, which uses GPRS (General Packet Radio System). The invention may also be used in other types of data networks, using packet switched traffic, e.g. the next generation mobile telecommunication system UMTS. The improvement of the quality of service is attained by defining a number of operator specific parameters, which give better possilibity to monitor and control of the quality of service within an area or for a given user. These parameters are then used by the operator in order to give the user better service. Using this invention the operator may in a better way attain the promised quality of service, both on user and area basis.