Abstract: Process for the preparation of permanently self-extinguishing cellular maials essentially comprising brominated unsaturated polyester resins, containing conventional additives, having a density comprised between 300 and 700 g/l correlated to a resistance to compression, as of a formed product, higher than the curve shown in the attached FIG. 1, said process being characterized by the fact that a brominated unsaturated polyester resin, containing an amount of bound bromine comprised between 10 and 30%, preferably between 12 and 25% by weight, containing conventional additives, is subjected to foaming by mechanical incorporation therein of a gas or a gas mixture, until crosslinkable liquid foams are obtained, which latter are subsequently subjected to crosslinking by conventional methods. The present invention further refers to permanently self-extinguishing cellular materials thus obtained.