Background: Tobacco consumption is the second major cause of death and the fourth most common risk factor for diseases, worldwide. Epidemiologic studies have traced the use of alcohol, tobacco, and illicit substances among medical students and physicians. Objectives: The current study aimed to investigate the prevalence of cigarette smoking and the related factors among the students of medical sciences in Mashhad University of Medical Sciences, Mashhad, Iran. Patients and Methods: This cross-sectional study was conducted on 946 health professional students in Mashhad University of Medical Sciences (MUMS, Iran) in autumn 2008. A standard self-administered questionnaire consisting of socio-demographic data, participant smoking status, family and peer smoking, attitudes and beliefs about smoking, awareness of cigarette negative effects and reasons for smoking cessation was used in the current study. Results: Among the students, 18.3% reported having ever tried or experienced with cigarette smoking. The overall prevalence of cigarette smoking was 9.8% with significant differences in prevalence rates by gender, 17.6% among males and 4.2% among females. Starting and continuing smoking was significantly correlated with the family cigarette consumption habits. The most common reason to start smoking was friends (24.9%) and the most important reason to continue smoking was personal life distress (17.6%). The majority of participants (92.3%) reported that they were aware of the hazards of smoking. A significant difference regarding awareness of smoking hazards was observed between smokers and non-smokers. The most important preventive factor for cigarette smoking was religious beliefs (69.1%). Conclusions: Although the prevalence of regular smokers among health professions students of MUMS was lower than general populations, but this level is still alarming and points at the rapid growth of cigarette use, especially among female students. Medical schools should work harder to tackle this phenomenon and address it more efficiently in their curricula.