The literature presents evidence that bidding firms acquiring privately held targets earn positive and higher abnormal returns on M&A announcements than those acquiring publicly traded firms (Chang, 1998; Hansen and Lott, 1996; Fuller, Netter, and Stegemoller, 2002; Moeller, Schlingemann, and Stulz, 2004; Faccio, McConnell, and Stolin, 2006). Faccio et al. (2006) refer to this phenomenon as the “listing effect” in acquirers' announcement period stock returns. Some literature on the Korean data claims that the listing effect on acquirers' returns is also found in the Korean stock market (Kim and Seo, 2000; Oh and Song, 2008; Jung, 2010). For example, using the sample of merger announcements in the Korean stock market over the 1980 to 2007 period, Jung (2010) examines the cumulative abnormal returns (CAR) of acquirers' stocks for 10 days from -5 to 5 surrounding announcements of merger deals and finds that bidders acquiring a publicly traded company have an average CAR of 0.13%, which is not statistically different from zero, whereas bidders acquiring a privately held company have an average CAR of 3.71%, which is significantly different from zero. Jung (2010) also shows that the average CARs of the two groups are significantly different from each other at the 1% level. Chang (1998) provides three explanations for the listing effect on acquirers' returns: the limited competition hypothesis, the monitoring hypothesis, and the information hypothesis. The limited competition hypothesis states that if the competition for private firms in the takeover market is limited, bidders can experience positive abnormal stock returns because the likelihood of underpayment is high. The monitoring hypothesis is related to the concentrated ownership of private firms. Private firms are typically held by a small number of shareholders. Therefore, when a bidder acquires a private firm through common stock exchange, the shareholders of the private target firm can become outside blockholders after the merger and may then become active monitors who contribute positively to firm value. Lastly, the information hypothesis explains the listing effect on acquirers' returns through the mitigation of information asymmetry. The relatively few shareholders of a private target firm have incentives to actively assess the prospect of a bidding company, and their willingness to hold the shares of the bidder conveys favorable information about the bidder to the market. The main purpose of this paper is to revisit the listing effect on acquirers' returns in the Korean stock market because prior studies on this issue do not explicitly separate the effect of backdoor listing (reverse takeover) from the listing effect on acquirers' returns. Backdoor listing means that a private firm merges with a listed firm and becomes public without going through an official IPO process. Many papers report that listed firms engaging in backdoor listing experience positive abnormal returns upon the announcement of the deal (Gleason, Rosenthal, and Wiggins, 2005: Park, Park and Bae, 2009; Kang, 2009; Kang and Kim, 2009). We refer to this phenomenon as the backdoor listing effect. In addition, Gleason et al. (2005) and Park et al. (2009) find that listed firms in backdoor listing are typically small and poor performers. Even though a private firm essentially acquires a listed firm in the backdoor listing process, on the surface, the listed firm survives and maintains its listing status throughout the merger process. When Korean listed firms file disclosure documents regarding backdoor listings with the Korean financial supervisory [Please check whether this should be “Korean financial supervisory.”], they classify themselves as acquirers and the essentially acquiring private firms as targets. Therefore, unless researchers pay particular attention, it is likely that backdoor listings are mistakenly treated as the mergers of private firms with public firms. If the sample of mergers of private firms includes backdoor listings, the results on the listing effect on acquirers' returns can be misleading. To address this concern, our study manually identifies backdoor listings among merger announcements and investigates the listing effect on acquirers' returns with and without the backdoor listing effect. We find that the cumulative abnormal returns are higher for acquirers of private targets than for acquirers of public targets only when we include backdoor listings in the sample of mergers of private firms. Excluding backdoor listings, we do not find that the listing status of target firms plays a significant role in acquirers' returns in merger announcements. Using multivariate tests to control various firm and deal characteristics, we also find that a target firm's listing status does not affect acquirers' returns, whereas backdoor listing has a significant impact on acquirers' returns. We perform robustness tests, considering the change in the regulation on the disclosure of backdoor listing and the monitoring effect of new blockholders, and find that the result of the non-existence of the listing effect remains the same. Therefore, the findings of our study suggest that the backdoor listing effect may have resulted in the erroneous conclusion by prior studies that a listing effect on acquirers' returns exists in the Korean stock market.