[en] In the paper the mathematical methods for dead-time and pile-up corrections are discussed. The dead-time correction formulae for a system of two short-lived isotopes and constant component (background) are reported which mathematical problem has not been solved so far. The new electronic circuit for simultaneous measurements of clock- and live- (or dead-) times is described. It is shown that using this circui circuit one can correct the counting loss for both effects simultaneously. Finally, the advantages and disadvantages of mathematical methods for dead-time and pile-up corrections are discussed based on the several year laboratory practice. (author)