In this paper, the authors present a methodology for the modelling and optimization of multi-service radio access for Universal Mobile Telecommunications System (UMTS) networks. The paper provides a description of the basis for modelling of a tandem pair: a Wideband Code Division Multiple Access (WCDMA) interface and an interface. The models involved in the study take into consideration a possibility of setting priorities to a number of selected traffic classes. Particular attention is given to the development of simple computational algorithms that would make it possible to determine the blocking probability for call streams with different priorities. The results of the analytical calculations are then compared with the results of simulation experiments, which confirm the high accuracy of the proposed analytical solutions.