This paper examines short-run and long-run performances of Employee Stock Ownership Plans (ESOPs) executed during 2002?2004 in Korea. We compare two representative methods acquiring shares allowed in ESOP; preemptive right vs. market purchase. First of all, an event study using market model was accomplished to analyze short-term effect. Then, we carefully investigate long-run abnormal performances. To control biases arising in measuring long-run abnormal performances, we employ several alternative measures of benchmarks and return calculations. Our study provides two important conclusions. First, in the short-run, the result of event study shows that there is an abnormal return decline around the acquisition date for the stocks acquired by preemptive right. Second, in the long-run, statistically significant positive abnormal returns for the stocks acquired by market purchase are observed for all alternative measures of benchmarks and return calculations. The evidence suggests that the employees may have more information than outsiders about long-term prospect of their firms.