Today in the era of wireless technology, everything seems to be possible. One of the wireless techniques that made the things easier is Zig-Bee technology. Zig-Bee is a wireless personal area network (WPAN) based on IEEE 802.15.4 standard to provide communication in short distance with low data rate in low cost. Zig-Bee 802.15.4 WPANs are made up of end devices, routers and a co-ordinator by using one of the three topologies which are star, tree and mesh topology. These networks have a wide range of areas where they perform spectacularly. These are the network when once deployed, need not any maintenance. This research work aims to have comparative analysis of network performance in star topology and mesh topology of a WPAN.