In the Polish public debate, one occasionally hears voices advocating the need for a significant change in the system of elections to Sejm, the Lower Chamber of Parliament – the objective of such changes would be to strengthen larger parties. As an example to follow, proponents of these changes cite Hungary, where the changes in electoral rules allowed the party in power to retain majority in the legislative despite reduction in popular support. Opponents of this solution see it as a manifest electoral manipulation. The aim of the present paper is to analyze how the “marginal only” changes to the structure of constituencies electing members of Sejm postulated in the political arena would affect electoral results of individual political groups and what would be the broader political consequences. The author pays particular attention to expected impact of such changes on the majority bonus for the winning party, possible government coalition variants, concentration of party system at parliamentary level and proportionality of elections. Simulation of allocation of seats in Sejm based on votes cast was prepared for three possible variants of the structure of Sejm constituencies, on the basis of historical data (for the 2011 and 2015 elections) and the predicted results of 2019 elections. Comparison of the simulated outcomes with the results obtained in the system currently in place allows to answer the main question posed.