Initial public offerings (IPO) have been attracting remarkable public attention since the late 1990s, especially during the dotcom bubble years. Despite their positive role in creating new companies, IPOs have been connected with many controversies and unsolved questions. Because of that, IPOs have been a subject of significant academic attention, and most articles have been focused on the major issues relating to: hot markets, underpricing, and long-run performance. This paper presents a theoretical overview, supported by an empirical study, based on the largest IPOs in Poland and the US, between 2000 and 2005, focusing on the un-derpricing and the long-run performance phenomenon. The observed period was chosen particularly in order to avoid the dotcom bubble and the financial crises years. Thus, the period was chosen in order to avoid the data being affected by the positive effects of the dotcom bubble, characterized by spectacular returns, as well to avoid the data being affected by the negative effects of the financial crises, characterized by a significant and sudden decrease in the stock market capitalizations. Poland was chosen for the study because of its remarkable performance during the crisis, and because of the fact that Poland has built a successful financial sector, which has gained the importance extending beyond the national level. The US was, on the other hand, chosen because it remains the biggest IPO market in the world. (fragment tekstu)