Despite awareness of the important role of motivation in second/foreign language (L2) learning, a thorough investigation into the motivational influence on the L2 writing processes and products has been neglected. In an attempt to fill this research gap, the present study explored the effects of different types of L2 self-related motivation (ideal and ought-to L2 selves) drawn from the theory of the L2 motivational self system (Dörnyei, 2005) on writing strategy use and writing quality. Sixty-eight Korean undergraduates with a low level of overall English proficiency responded to questionnaires designed to measure their ideal and ought-to L2 selves and writing strategy use. They also completed a descriptive composition task aimed at assessing their writing quality. Regression analyses revealed that the ideal L2 self had a significant positive effect on both planning strategy use and writing outcomes, whereas the ought-to L2 self was merely correlated with revising strategy use. This study provides some empirical support for the potential of an idealized future L2 self-image to become a major determinant of writing processes and products. The results are discussed with reference to a promotion/prevention focus and a sensitivity of the ideal and ought-to L2 selves to positive/negative learning outcomes.