This study explored the relationships among preservice teachers' conceptions of teaching using mobile devices and the quality of technology integration in lesson plans. A total of 47 preservice teachers in Taiwan who had experienced designing their own lesson plans and teaching materials (ie, eBooks and applications) for teaching using mobile devices (ie, smart phones and tablet PCs) participated in this study. The results showed that four qualitatively different conceptions of teaching using mobile devices were identified, namely "technology support," "knowledge transmission," "learning facilitation," and "supporting students to learn." This study also found that the teachers who had more constructivist perceptions of teaching using mobile devices, such as facilitating students' understanding in a convenient way or supporting student learning in a more active way, appeared to attain better quality technology integration in their lesson plans than those teachers with traditional conceptions.