Öz Using of different chemical modifiers in the determination of some elements in copper concentrates by ETAAS has been proposed. Different ammonium salts (ammonium molibdate, ammonium vanadate, ammonium nitrate, ammonium sulfate and ammonium dichromate), Ba(OH)2, H3BO3, and V2O5, compared with Ni(NO3)2 as a classical modifier for thermal stabilization of selenium were investigated. It was found that ammonium dichromate give the best results as a modifier. In presence of ammonium dichromate, pyrolysis temperature was extended up to 1100 oC. In the atomization stage, a constant absorbance was obtained between 1900 and 2300 oC. After preliminary investigation, the method for determination of selenium in copper ores and concentrates was developed. Limit of detection of 1 ng/ml Se was achieved, without preconcentration of Se or separation of sample matrix