The purpose of this study was to examine how Korean science and engineering students view English-medium instruction (EMI) and Korean-medium instruction (KMI). The participants were 174 undergraduate students enrolled in EMI and KMI classes offered by the same instructor at a Korean science and engineering school. Interviews and questionnaire surveys were conducted, and students' course evaluations, English scores and course grades were compared. The results of a campus-wide undergraduate student survey on EMI were also analyzed. The findings of the study show that the KMI-class students demonstrated higher levels of satisfaction and better performance in their classes than the EMI-class students did. Only 22% of the students in both classes found EMI classes helpful for improving their English ability. Nevertheless, the majority of the students supported the school's maintenance of an EMI policy. In the conclusion, the paradoxical attitude of the students and the implications of the study are discussed.