A MALDI-ToF investigation of furanic foams before and after carbonization at 900°C has been carried out. Comparison between MALDI-ToF spectra, before and after carbonization, shows how original building blocks of the network are modified, rearranged or survived during the process. Even if most of the constituents are transformed to more stable aromatic structures, some of the starting compounds resist intact the process of carbonization. The results appeared to indicate that some furanic oligomers are particularly stable and unaffected by carbonisation. The hypothesis that these may be cyclic furanic oligomers has been checked by molecular mechanics calculation of their relative energies.