The objectives of this work were to study the PCDD/F emissions during the co-combustion of waste wood/coal in an industrial boiler and to determine the relation of the toxic emissions to the fuel properties. Co-combustion experiments were performed in a 13.8 MWthermal industrial moving grate combustor. The fuels, which were examined in this study, included Greek lignite, natural uncontaminated wood, power poles and medium density fibers (MDFs), which were by-products of the plant production process. Fuel blends were prepared by mixing single components in various concentrations. PCDD/F emissions were collected during experimental runs and were analysed according to standard methods. Low PCDD/F emissions were obtained during the co-combustion tests, lower than the limit value of 0.1 ng TEQ/Nm3. The lowest values were observed during the combustion of fuel blends containing MDF, possibly due to the inhibitory action of some of the N-containing MDF ingredients, such as urea. No direct correlation was found between the PCDD/F and the copper emissions, while examination of the PCDD/F homologue patterns revealed the predominance of the lower chlorinated isomers over the higher ones.