Alongside the Senate, the Sejm of the Republic of Poland is one of Poland's two main lawmaking organs. The author characterises the functions of the Sejm, defining them in terms of the fundamental directions of its operations. Mention is made of an assumption regarding the basis of each of the Sejm's prerogatives. The execution of the following duties falls within the competence of the Chamber of Deputies: the shaping of the political regime, law making, budgetary matters, the acceptance of international law and the establishment and closure of state organs and organs of supervision. The shaping of the political regime is a very important function of the Sejm, giving it, together with the Senate, the possibility of voting in changes to the constitution. Taking into consideration the complexity of the legislative procedures, the author devotes considerable attention to presenting this aspect of the Sejm's competence, which it carries out in conjunction with the upper chamber, the Senate. Focus is also placed on the task of the establishment and closure of state organs, which is performed by the Sejm and which is also known as a 'creative function'. This is of extraordinary importance, particularly in the case of appointing a new government as, without receiving a vote of confidence from the Chamber of Deputies, a government is unable to function in practice. The Sejm plays an essential role when it comes to acting in a supervisory capacity with regard to the organs of state. Amongst the many powers with which the constitution endows the Sejm is the possibility of passing a constructive vote of no confidence against the entire Council of Ministers, as well as that of dismissing an individual minister for his actions the department he or she heads. The author also gives consideration to the Sejm's performance in the capacity of accepting international law, which, in the contemporary, globalised world, is beginning to play an increasingly important role.