The aim of the paper is to analyze the economic effectiveness of public and private sectors in the period between 1989-2004 in connection with the progressing changes in property structure in Poland in that period. The analysis was conducted on the macro and mezo levels. The method of relative comparisons, used by the authoress, involved juxtaposing the contributions of public and private sectors in the gross added value, the number of the employed, the value of fixed assets and the value of production inputs. The calculation of relative labour efficiency, productivity of capital, effectiveness of production inputs and relative labour costs enabled her to verify the thesis of the effectiveness of Polish privatization. The achieved results indicate that in most cases privatization positively influenced the economic effectiveness of the relevant areas of economy. It is especially visible in the analysis of relative effectiveness of joint capital and labour inputs and relative efficiency of labour . The paper confirms the thesis of more effective functioning of private sector companies rather than public sector.