This article explores the intricacies of the ZigBee wireless protocol that works on the underlying IEEE 802.15.4 standard in order to fine-tune it in a way that will meet the unique requirements of a Wireless Body Sensor Network. This particular standard is relatively new and is specifically designed to offer low cost and power consumption, reliability, and inter-operability for sensor and control applications with low to moderate data rates. By simulating ZigBee wireless networks with the possible star, tree, or mesh topologies under different scenarios, the performance of each topology can be evaluated and assessed. The results from the simulations demonstrate that ZigBee wireless networks using the mesh topology have the highest overall performance regardless of the number of nodes. Moreover, the ratio of routers to end-devices in a Personal Area Network can either improve or deteriorate its performance.