The effective atomic numbers and electron densities of the CuGaSe2 semiconductor were calculated at 29 different energies from 6.9 to 511.0 keV by using the measured mass attenuation coefficients. Also, the mass attenuation coefficients for Cu, Ga, and Se elements were obtained at this energy range. The samples were irradiated using Cd-109, Co-57, Ba-133, and Na-22 radioactive sources. The x-ray energies were obtained using secondary targets. The gamma and x-rays were counted by an Ultra-LEGe detector with a resolution of 0.55 at 122.0 keV. The mass attenuation coefficients were compared with theoretical ones obtained using the XCOM program. Copyright (c) 2008 John Wiley & Sons, Ltd.