The efficient use of energy and resources is important from the point of environmental responsibility, but at the same time, it can be an opportunity towards obtaining economic value. Waste-to-energy (WtE) plants have the dual objective first to reduce the amount of waste sent to landfills, and second to generate electricity, heat and biogas. Tracking the flows of energy and materials within WtE system could be convenient optimization tool for waste treatment process. Through modeling and simulation of complex operating systems, it is manageable to present the actual operation states and conditions, and in case of modified operation conditions, possible treatment results. To achieve better operating performances chosen models can analyze, adjust and improve the WtE process in accordance to desired parameters. This paper gives an insight of some of the most adequate tools for modeling of WtE plants.