The paper presents some consequences of using semi-open lists, including the preferential vote mechanism, in parliamentary elections in Poland. The Authors discuss whose role in assigning parliamentary seats is greater: that of party organizations’ leaders, who decide on the order of candidates on electoral lists, or that of citizens who cast preferential votes. The paper focuses in the elections in the years 2001–2011, in which, according to poll data, party voting dominated over personal voting. The results of parliamentary elections in Poland show that ballot position effects are persistently present and that people tend to vote for list leaders in their constituencies. However, a simulation of a closed-list mechanism shows that in 2001–2011, ca 20 per cent of parliamentary seats were assigned as a result of the interventionist impact of the preferential vote on the
candidate lists established by parties. The ability to vote for a specifi c candidate is rather important for Poles. The Authors also point out that the candidates from the top of party lists may obtain such good results because voters resort to simple reasoning and vote for those from the top of a list, irrespective of the nature of the list itself. (However, the effect does not seem to be very signifi cant).