The present invention relates to a self-extinguishing polymeric composition comprising: a) a stabilizing polymeric composition containing i) from 80% to 99.5% by weight of one or more vinylaromatic polymers compatible with each other; and ii) from 0.5% to 20% by weight of at least one block copolymer containing: 1) at least one vinylaromatic polymer block compatible N with (i) and constituting a weight quantity equal to or higher than 15% by weight with respect to the whole block copolymer, and 2) at least one vinyl copolymer block containing epoxy groups so that there is from 0.7% to 19% by weight of oxirane oxygen calculated on the total of block copolymer; and b) from 0.03 phr by weight to 10 phr by weight, calculated on the basis of component (a), of at least one halogenated flame retardant.