In this work, fly ash and solid residues produced by an incinerator of Refuse Derived Fuel (RDF) have been analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and heavy metals. Furthermore, the content of that species in the fly ash and the concentration of hydrochloric acid and particulate in the gas stream have been tested before and after the flue gas treatment system (wet scrubbing type) to determine the efficiency of the system. Chemical analysis of the extracts have been performed by high resolution gas chromatography with mass-spectrometric detector (GC-MS) and atomic absorption spectroscopy. A description of the incinerator plant and of the flue gas treatment system is presented. The results are critically discussed.