In this paper we study the expected difference between the QoS classes in an ad hoc network. The results have a direct bearing on the suitability of extending a fixed DiffServ architecture into an ad hoc network. Through simulation, we analyze the number of classes that can be used in the ad hoc network with separation between the observed QoS in the different classes. The results clearly depend on the type of traffic run in the network. With well behaved CBR traffic, the ad hoc network supports no more than four classes, but with more aggressive traffic like TCP no more than two classes are supported. In addition, there is a fairness problem; the performance for a particular flow is not well distributed among the nodes.