Internet access via mobile communications networks is growing rapidly; NTT DoCoMo's Internet access service using cellular phones, known as i-mode and started in February 1999, is no exception. The i-mode service enables the user to send e-mail and access Web sites for a variety of information through simple operation of a mobile terminal equipped with a browser. As a result, the traffic to be carried by the PDC (Personal Digital Cellular)-- Packet mobile communication network, which is used to provide the i-mode service, is also increasing rapidly. To meet this growing demand, the switching systems in place are being either increased in capacity or replaced by more powerful ones. To plan this effectively, it is necessary to make an accurate evaluation of the i-mode processing capacity. We have developed a new method of evaluating processing capacity, which is based on the conventional method but takes account of the characteristics specific to the PDC-Packet network. This paper discusses the method of evaluating the processing capacity of switching systems used in the PDC-Packet mobile network.