This study investigated how Korean EFL learners' attentional allocation changes during task repetition with or without self-reflection and how this change affects their task performance. A total of 30 Korean high school students were divided into a task repetition only group, a task repetition with self-reflection group, and a comparison group. Each group repeated the same picture-based storytelling task according to its group condition and then performed a new task. Participants' task performances were analyzed in terms of fluency, complexity, and accuracy and their retrospective interviews were categorized in order to explore their attentional allocation during task planning and performance. The results demonstrated that the learners placed most attention to conveying the message while planning and performing their first task. However, when repeating the same task, the learners paid more attention to structures and forms leading to improvement in complexity and accuracy. These learners were also more likely to employ strategies they had learned previously when doing a new task, which was helpful. Self-reflection raised learners' awareness on the target form and positively influenced accuracy.