In this paper, we propose an analytical model to evaluate the hidden station effect on the performance of the IEEE 802.11 Distributed Coordination Function (DCF). DCF is a random channel-access scheme based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) method and the binary slotted exponential backoff procedure to reduce the packet collision. Most collisions are caused by hidden stations because stations cannot sense each other's transmission and often send packets concurrently, resulting in significant degradation of the network performance. The proposed model generalizes the existing work on 802.11 DCF performance modeling. The performance of our model is evaluated by comparison with NS-2 simulations. The impact of different parameters, such as the number of station, packet size and initial backoff window size, is also considered.