Plasma gasification/vitrification is an innovative and environmentally friendly method of waste treatment. A demonstration plasma gasification/vitrification unit was developed and installed in Viotia region in order to examine the efficiency of this innovative technology in dealing with hazardous waste. The preliminary results from the trial runs of the plasma unit, as well as the study of the influence of certain parameters in the system performance are presented and analyzed in this paper, contributing to the improvement of the operation performance. Finally, data on the final air emissions and the vitrified ash toxicity characteristic leaching procedure (TCLP) results are provided in order to assess the environmental performance of the system. The produced slag was found to be characterized by extremely low leaching properties and can be utilized as construction material, while the values of the polluting parameters of the air emissions were satisfactory.