Capillary gas chromatography proved useful for characterizing naphtha produced from coprocessing coal and heavy oil at various conditions. Increasing the coal concentration in the feedstock resulted in higher contents of phenols, indane and cyclohexanes in the naphtha product. Increasing the reaction temperature resulted in higher contents of phenols and indane, indicating a greater contribution of coal to the naphtha product at higher severities. The combined use of hydrogen sulphide and iron sulphate as promoter resulted in higher contents of indane, alkanes and cycloparaffines in the naphtha than the use of either alone.