Abstract Co-pyrolysis of LignoBoost ® lignin with synthetic polymers (polyethylene, polypropylene, polystyrene and polycarbonate) was performed in a semi-batch reactor at 500 °C and self-generated pressure. The mass yields and composition of degradation products were determined in order to identify the interactions between components. Generally the degradation of lignin is slightly diminished while that of synthetic polymers is enhanced. Particular behaviour was observed for co-pyrolysis of lignin and polycarbonate, both materials having phenol-type structure. The stronger interactions between components in this case led to higher amounts of pyrolysis oil, which had simpler composition.