In the article, the authors compare the institutions of the Senate of the Second Polish Republic on the basis of the Constitutional Act of March 17, 1921 and the Constitutional Act of April 23, 1935. In the first part, the article presents the the way of functioning and selecting the senators in accordance with the provisions of the Constitutional Act of March 17, 1921. The second part of the article is a description of the regulations contained in the constitutional Act of 23 April 1935, on the basis of which then Senate of the Republic of Poland functioned. At the end of this article, the authors indicate similarities, but above all differences, in the functioning of the first chamber of the parliament of the Second Polish Republic.W arty...