A method for treating vapours generated during the pyrolysis of carbon fibre composites, such as production waste generated by the producers or composites of carbon fibre at the end of the service life thereof, includes, passing the vapours through a reactor which is at a high temperature and contains a solid material filler (solid bed), for example CSi, and optionally also a solid catalyst having an acid and/or reforming function, preferably both, for example a transition metal supported on an acid substrate, such as Ni on zeolite. Following the condensation of the vapours resulting from the treatment, an improved aqueous liquid phase, a minimum or non-existent organic fraction and a gaseous phase of increased added value are obtained.