Once expandable polystyrene (EPS) foam has been used out, its high volume-to-weight ratio becomes a serious problem, and it is now prototypical high-bulk/non-burnable landfill problem. This is one of main obstacles for EPS foam to be recycled. This paper is concerned with volume reduction method for wasted EPS foam. The analysis is focused on the description of importance of volume reducing method for EPS foam. Wasted EPS foam has not been recycled effectively since its volume to weight ratio is extremely high. The large volume of EPS has prevented from its proper recycling because of high cost of transportation to recycling plant. In this reason, successful recycling of wasted EPS foam results directly from successful volume reduction of wasted EPS foam in proper manner. This paper deals with various existing methods for volume reduction of wasted EPS foam. Six existing processes of volume reduction for wasted EPS has been analyzed qualitatively and compared each other in terms of expected polystyrene (PS) characteristics after volume reduction, cost effectiveness of each process, possible effects on environment caused by the volume reduction process, and applicability to possibly recycled products. The methods analyzed in this paper include thermal, solvent, far infrared, pulverization, and mechanical compaction. Analysis was concentrated to compare each process mostly in qualitative manner among existing processes.