PURPOSE: To produce high melting hexabromocyclododecane product useful as a noncombustible agent by the selective recovery of hexabromocyclododecane of a preferred isomer ratio.

CONSTITUTION: (1) Bromine and cyclododecartriene are mixed in a solvent containing an alcohol and a halogenated hydrocarbon, and the resulting reaction product is kept at a temperature ≥40°C, with a load factor ≥40$, and at a halogenated hydrocarbon/alcohol weight ratio of 3/97-90/10 until a solid phase comprising at least a first kind of particles rich in a first hexabromocyclododecane isomer and a second kind of particles rich in another or other isomers thereof are formed. (2) In order to contain preferentially the first kind of particles in said product, the two kinds of particles are separated according to their sizes or weights.