Tehran University of Medical Sciences Journal of Sleep Sciences 2476-2938 4 1-2 2019 12 16 29 36 EN Omid Saed Department of Clinical Psychology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Reza Ahmadi Department of Clinical Psychology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Jahangir Mohammadi Baytamar Department of Clinical Psychology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Majid Mohammadi Department of Clinical Psychology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Zahra Kousari Department of Clinical Psychology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran 2018 10 21 Background and Objective: Insomnia is one of the most prevalent sleep-related problems among university students. To date, several explanatory models for insomnia have been presented; however, the perspective of procrastination has been less considered. The present study's aim was to determine the association between procrastinatory cognitions and bedtime procrastination, and insomnia among students. Materials and Methods: The present study was a cross-sectional study. The study population consisted of students of Zanjan University of Medical Sciences, Zanjan, Iran. A total of 433 students were selected using stratified random sam-pling method. Data were collected using the Insomnia Severity Index (ISI), Bedtime Procrastination Scale (BTPS), and Procrastinatory Cognitions Inventory (PCI). Results: The severity of insomnia in medical students varied from non-clinical to clinical insomnia. In addition, the results of regression analysis indicated that the full model was significant regarding the predictors of insomnia. Only 3% of variance in insomnia severity was due to demographic variables, while bedtime procrastination and procrastina-tory cognitions explained 33% of the variance in the severity of insomnia among students. Conclusion: The procrastination-related structures such as procrastinatory cognitions and bedtime procrastination play an important role in explaining insomnia in students. Addressing these variables as perpetuating factors can be consid-ered in the treatment of insomnia in students. https://jss.tums.ac.ir/index.php/jss/article/view/114