The present invention relates to a styrenic polymer composition comprising a flame-retardant effective amount of a compound of formula (I): (C.sub.6H.sub.(5-n)Y.sub.n)CH.sub.2X, wherein X is Cl or Br; Y is Cl or Br; and n is an integer between 1 and 5; or a mixture of two or more of said compounds of formula (I) or their homologues and derivatives or other Br-FRs.