One of the most fundamental issues in studies on voter turnout is its stability. The more stable citizens’ attitudes and behaviours, the healthier and more predictable the democratic system. Knowledge why voting is stable/unstable helps to understand the whole puzzle of voter turnout. Thus the main purpose of this paper is to analyze the issue of voter turnout stability in a very specific context of Polish parliamentary and presidential elections of 2005, when citizens were called to the polling stations three times every two weeks. Polish National Election Study panel dataset gives a unique opportunity to examine this issue in a more in-depth manner. The main finding of the paper is that many Polish citizens are rather unstable, both in long-term and short-term perspective. And although majority of the electorate still behaves in a stable manner, the number of unstable citizens is quite high, and, what is even more alarming, it tends to increase, which can imply serious challenges to democratic system.