Recycling carbon fiber from residual carbon fiber reinforced plastics (CFRP) is one of the key aspects of the future in the field of waste management. This work presents the possibility of recovering chemical compounds through the thermo-catalytic treatment of the gases and vapors produced from the decomposition of the polymeric resin that takes place in the recycling of CFRP by pyrolysis. A lab-scale installation consisting of two reactors placed in series has been used for the experiments. In the first reactor, pyrolysis of poly(benzoxazine)-based composite waste has been carried out at 500 °C. In the second reactor, the thermo-catalytic treatment of gases and vapors has been performed at 900 °C in the presence of a commercial and a lab-prepared reforming catalyst. The thermal treatment of gases and vapors leads to a significant reduction in the collected liquids and a H₂-rich gas fraction. When reforming catalysts are used, the organic fraction of the liquids is virtually eliminated and gas fractions containing more than 50% H₂ in volume are generated. The results obtained show that it is possible to valorize the material content of the polymer resin, which represents an important advance in the recycling of CFRP by pyrolysis.