In this paper, impact of changes in parameters of offered traffic on the accuracy of determining the parameters of overflow traffic in hierarchy systems with multi -service traffic was presented . Pascal type traffic streams were offered to the considered systems . The study investigated the impact of changes in the number of sources , intensity of traffic offered by individual classes , as well as changes in the traffic offered by single free source . The presented results are based on determined relative errors of the values of overflow traffic obtained in simulations and on the basis of calculations .