The authors start with the presentation of two retirement systems: before and after the reform. They show how pensions are calculated in both systems. The article examines changes in the replacement ratio resulting from the 1999 reform of the Polish pension system. Retirement benefi ts are estimated for eight hypothetical individuals, men and women, with different levels of earnings. As retirement benefi ts are the function of, among others, the future life expectancy, the paper illustrates the differences in estimates resulting from the application of two different life table perspectives: period and cohort. The defi cit of the statecontrolled pay-as-you-go component (the "fi rst pillar") of the pension system is estimated under the assumption that the calculation of benefi ts involves the current period life tables of the Central Statistical Offi ce (GUS).