in health-screening programs. If attitudes related to health behavior can be identified, health protection interventions for attitude change can be developed, and an increase in desirable health behavior would result (Champion 1984). The HBM is composed of six concepts: 1) perceived susceptibility (a person's opinion regarding the chances of developing a condition). 2) Perceived Severity (one's belief regarding the seriousness of a condition), 3) barriers (one's beliefs regarding the total barrier costs of implementing the recommended action), 4) benefits (the opinion of the effectiveness of actions to reduce the risks of a condition), 5) health motivation related to performing the health behaviors, 6) self efficacy (one's beliefs about their capabilities to take the recommended action) (Ueland et al., 2006). The HBM-based research studies have determined these components of HBM as correlates of cancer prevention and screening behaviors (Janz et al., 2003;Palmer et al., 2007; McFarland 2013; Ebu et al., 2015). 8372Various studies have sought to identify psychosocial factors associated with participation in CRC screening (Gili et al., 2006; Cole et al., 2011; Gonzalez et al., 2012; Jorgensen et al., 2013). But few studies have examined beliefs and behaviours related to CRC screening in Iranian population. A previous study about beliefs associated with CRC screening in an Iranian adult population based on preventive health model, showed that subjects mostly reported poor attitude about CRC screening (Salimzadeh et al., 2011). Javadzadeh et al found a significant relationships between knowledge and all domains of HBM excepting perceived benefits among individuals more than 50 years old (Javadzade et al., 2012).It is necessary to identify the factors associated with colorectal cancer screening adherence to increase this adherence (Gimeno García, 2011). As well, since adherence to CRC screening could be influenced by culture (Wang et al., 2006), identifying these factors in different cultures is useful to better understanding of people's beliefs which assist us in developing ways to increase use of CRC screening procedure (Brennenstuhl et al., ). Also effective cancer screening programs depends on accurate assessing patients' needs and designing helpful educational strategies. The purpose of this study was to determine the predictive factors of CRC screening adherence among Iranians aged 50 and older based on the HBM. Materials and Methods Design and participantsThis cross sectional study has been performed in June 2012 to May 2013 in Qom City, a provincial city in the central region of Iran. A convenience sample of 200 individuals aged 50 and older was recruited from population at outpatient clinics in three teaching hospitals. The inclusion criteria were being 50 years or older, not having had CRC and ability to communicate in Persian language. Verbal informed consent was obtained from the participants after the purpose of the study was explained to them. The questionnaire's items were read for those individual...