The X-rays attenuation coefficients for Cu, In and Se in elemental state and the semiconductor CuInSe2 were measured at 15 different energies from 11.9 to 37.3 keV by using the secondary excitation method. Monochromatic photons were obtained using the following secondary targets: Br, Sr, Mo, Cd, Te and Ba. 59.5 keV gamma rays emitted from an annular Am-241 radioactive source were used to excite secondary target and X-rays emitted from secondary target were counted by a Si(Li) detector with a resolution of 0.16 keV at 5.9 keV. A method to determine the thickness of thin film with XRF is described. Additionally, the effect of absorption edges on effective atomic numbers and their variation with photon energy in composite semiconductor sample was discussed. Obtained values were compared with calculated values. (c) 2006 Elsevier B.V. All rights reserved.