This study examined the effect of firm performance on CEO turnover using a sample of non-financial firms listed on the Korea Stock Exchange and KOSDAQ between 1987 and 2001. Considering the characteristics of Korean firms, where CEOs are often controlling shareholders and large business groups (chaebols) exist, this study analyzed how the effect of firm performance on CEO turnover differs between professionally managed firms and chaebol-affiliated firms. The results found that owner-managers are more difficult to replace compared to professional managers even when firm performance is poor. However, no statistically significant difference was found in the probability of replacing a poorly performing CEO between non-chaebol firms and chaebol-affiliated firms.