There has been much discussion in Poland recently concerning the conceptions of the personal income taxation system. From time to time we can hear a new proposal calling for a replacement of the present progressive personal income tax with the flat one. The followers of the flat tax obviously point out to the advantages of the latter one, but it is interesting that none of the high economically developed states has opted for that solution so far. The main aim of the paper was to compare the two conceptions of the personal income taxation: the progressive one and the flat one, and to analyse the impact of either on the distribution of the present personal income. In the first part of the paper the main characteristics of the flat and progressive personal income tax are presented while in the second part the present tax scale is described against the nominal and effective related to it. Finally, the author makes a comparative analysis of the personal income tax scales existing in the OECD countries. The data used in the paper came from the information of the Polish Ministry of Finance.