Introduction & Objective: Sleep quality can affect human health and daily function. On the other hand, every person has relatively stable personality trait which lives with and has occupational, social and interpersonal interaction. Regarding the importance of sleep quality, and because less considerations have been devoted to correlation between sleep disturbances and personality traits, the present investigation was done. The purpose of this study was to determine personality traits and sleep patterns among medical students in Hamadan medical university and the relationship between traits inquestion sleep patterns as well.

Materials & Methods: This descriptive and Cross – Sectional study involving 150 randomly selected medical students. Pittsburgh questionnaire, MMPI and a checking list for demographic information were employed. Data processing and statistical analysis were performed using SPSS10.

Results: The findings of this study have showed that 48 percent of our cases have suffered from sleep disturbances. The number of personality traits such as narcissistic, histrionic and borderline (cluster B) observed among students had greater frequencies than other traits. The average of night and day sleep time was 8.95±2.01. No meaningful correlation has been found between sleep disturbances and personality traits in our cases.

Conclusion: A great number of medical students suffer from sleep disturbances, because it may highly affect student’s health and their daily function. More and wider studies should be done.