Mass attenuation coefficients of the YBaCuO and BiPbSrCaCuO superconductors were determined at 511,661, and 1274 keV photon energies. The samples were irradiated using 0.5 mCi Cs-137 and 2 mCi Na-22 radioactive sources. The photons crossing the samples were counted using a multi-channel analyzer with a NaI(Tl) detector. The Nucleus II software was used to analyze the spectra. It was observed that the mass attenuation coefficient decreases with increasing energy and increases with increasing atomic number. (C) 2004 Elsevier Ltd. All rights reserved.