BackgroundMobile instant messaging services are being increasingly used for educational purposes, but their effectiveness in medical education is not well known. We assessed whether students’ use of Kakao Talk (a mobile instant messaging service) during the early period of a week of clinical education influenced its use for academic purposes during a later period of the same week.MethodsThe online communication records of 151 third-year medical students (in 39 clinical education groups) who used Kakao Talk during clinical education were reviewed. The 39 groups were categorized as low, middle, or high according to the number of total chats (on all subjects, not just academic) per student over five days. The relationship between the number of total chats during the first two days and the number of academic chats during the last three days (of five-day chatroom weeks) was analyzed.ResultsThe number of total and academic chats over all five days, the first two days, and the last three days was highest in groups with the highest number of total chats per student. Similarly, the highest number of students posting total and academic chats was found in these groups. In addition, the number of academic chats per student and the frequency of questions raised by students were also highest in these groups. During the last three days, the number of students posting total chats was lower than that during the first two days, and the number of academic chats per student posting academic chats was higher. The number of total chats on the first or second day positively correlated with the maximum value of academic chats on the third to fifth days.ConclusionHigh frequency mobile instant messaging use early on in clinical education might encourage its use for academic purposes during later periods.