There are two ways of becoming listed firms for unlisted firms. One is initial public offering(IPO) and the other is backdoor listing(BL). The BL has simpler listing requirements andprocedures than the IPO. Unlisted firms with short history, small firm size, high technology,and high growth rate can become listed firms through BL at a low cost and thus can enhancepublic recognition and increase financing capabilities. The BL can give diversification advantageand synergy effect to unlisted firms and can increase vigor for the stock market with thecombination of listed firms and unlisted firms. The research on the BL firms is at early stage, and it is hard to find a prior research inaccounting area. This paper investigates whether the earnings quality of the BL firms beforelisting is different from that of the IPO firms. This paper also examines the difference of theearnings quality of the BL firms prior to listing before and after 2006 when the regulations ofBL strengthened. As measures of earnings quality, this research uses persistence, predictability, earningsmanagement, and conservatism which were discussed in Dechow et al.(2010). The number ofBL firms analyzed in the paper is 221 which were listed in KOSDAQ from 2001 to 2010. Research findings are as follows. First, the earnings quality of the BL firms before listing islower than that of IPO firms. This implies that the unlisted firms having difficulty to meet thestrict IPO listing requirements and procedures may have chosen BL to enter the market. Second,the earnings quality of the BL firms before and after the 2006 regulations is not significantly different. The result means that the new quantitative requirements of the regulation for BL donot contribute to increasing the earnings quality of the BL firms. The findings of this paper will contribute to the studies on the BL which have been neglectedso far in accounting and finance area.