Treatment and recycling of Waste Electrical and Electronic Equipment (WEEE) become more and more regulated by laws and directives in several countries. Disassembly is the first step in this process and determines the results of the subsequent processes of mechanical treatment and recovery. In addition to the legislative background, disassembly of WEEE is also impacted by a framework of economical, ecological, technological and social factors. To ensure efficient disassembly processes, systematic planning and economical evaluation of disassembly systems comes into focus. At the IWF a six-step planning approach with recursion loops was developed to support the planning process of efficient disassembly systems. The approach was implemented in a software tool named "SiDDatAS" which links the eco-design tool ProdTect® and the material flow simulation software eM-Plant®.