Abstract Activities of the radionuclides 124Sb and 152Eu were determined by the efficiency extrapolation method applied to 4π(PC)−γ coincidence counting. The 124Sb sources were prepared from a solution with the chemical form of 50 μg g −1 SbCl 3 in 2 M HCl. To inhibit the volatility of antimony chlorides, the sources were slowly dried in a H 2S atmosphere with relative humidity of 76% for about 48 h. This procedure increased the beta detection efficiency up to 0.98, which simplified the standardisation. In the 152Eu standardisation, the optimal γ-ray energy window setting to achieve a linear dependency and the correct slope of the extrapolation curve were derived by means of software coincidence counting system using offline evaluation of data with different coincidence parameter settings. The results obtained by the software coincidence counting system were compared with those obtained by the conventional coincidence method.