2,2',3,3',4,4',5,5',6,6'-bromdiphenyl ether (BDE-209) solutions were irradiated with ultraviolet (UV) and electron beams. Organic compounds were fully removed by each type of radiation. The absorbed energy of the ionizing radiation (electron beams) needed for removal was much lower than that of UV photocatalysis. BDE-209 removal using the ionizing radiation was accelerated drastically by dosage. It is suggested that pH value of solution affect the decomposition rates. Radiolysis with the high pH value showed consistently high rate and high efficiency of BDE-209 removal.