ZigBee, known as IEEE 802.15.4 standard, is designed for Wireless Sensor Network (WSN) due to low power consumption and high reliability. The network layer can support star, tree and mesh topologies. In this work, cluster tree and mesh topologies are simulated in OPNET. Then through- put, delay and packet delivery ratio in direct transmission between source and sink are collected. Further, broadcast packets are simulated to show the influence of the packet interarrival time.