Liquid products obtained from pyrolysis of plastics and thermosets fractions (keyboard, casings and printed circuits board and their mixture) of used computers were upgraded by thermal and catalytic hydrogenation. The effect of thermal hydrogenation was improved by using catalysts such as commercial hydrogenation DHC-8 catalyst and metal loaded activated carbon. The upgraded degradation products were separated in three fractions (residue, liquids and gases) and characterized by suitable methods such as gas chromatography (GC-MSD, GC-AED), infrared (FT-IR) and H-1-NMR spectroscopy, elemental analysis, etc. Using of catalyst mainly affected the product distribution of upgrading process. Liquids having high amount of aromatics were obtained by upgrading. Most of hazardous toxic compounds in liquids were eliminated after hydrogenation (e.g., halogens were removed mainly by converting them into gaseous hydrogen chloride and bromide). It has been established that the hydrogenation led to elimination of the most of hazardous toxic compounds, mainly those containing bromine. (c) 2006 Elsevier Ltd. All rights reserved.