An experimental study on co-gasification of woody biomass and coal in oxygen-containing atmosphere was carried out in a pressurized fluidized bed reactor. The wood used was birch from a Swedish paper mill, while the coals used were Daw Mill coal of UK origin and a bituminous coal from Poland. The operation temperatures were 900 and 700 degrees C, and the pressure was 0.4 MPa. The ratio of coal to wood was varied in the investigation. The study was focused on possible synergetic effects in the thermochemical treatment of the fuels. The char formed was examined. The tar produced in the process was analyzed. The nitrogen compounds emitted were detected. A noticeable phenomenon was that the mixtures of the fuels and their char formed in situ demonstrated an unexpected high reaction rate of gasification under the studied conditions. The yield of char diminished and consequently the production of gas increased. Further, both the formations of tar and nitrogen compounds also seemed affected synergetically in the co-gasification experiments of the fuels. The yields of tar and of ammonia were lower than expected.