Colorectal cancer (CRC) is now common in Thailand with an increase in incidence over time. Health authoritiesare planning to implement a nationwide CRC screening program using fecal immunochemical test (FIT) as aprimary screening tool. This study aimed to estimate preferences and acceptance of FIT and colonoscopy, explorefactors influencing the acceptance, and investigate reasons behind choosing and rejecting to screen before theprogram was implemented. Patients aged 50-69, visiting the primary care unit during the study period, wereinvited to join this study. Patients with a history of cancer or past CRC screening were excluded. Face-to-faceinterviews were conducted. Subjects were informed about CRC and the screening tests: FIT and colonoscopy.Then, they were asked for their opinions regarding the screening. The total number of subjects was 437 (86.7%response rate). Fifty-eight percent were females. The median age was 58 years. FIT was accepted by 74.1% ofsubjects compared to 55.6% for colonoscopy. The acceptance of colonoscopy was associated with perceivedsusceptibility to CRC and family history of cancer. No symptoms, unwilling to screen, healthy, too busy and anxiousabout diagnosis were reasons for refusing to screen. FIT was preferred for its simplicity and non-invasivenesscompared with colonoscopy. Those rejecting FIT expressed a strong preference for colonoscopy. Subjects chosecolonoscopy because of its accuracy; it was refused for the process and complications. If the screening programis implemented for the entire target population in Thailand, we estimate that 106,546 will have a positive FIT,between 8,618 and 12,749 identified with advanced adenoma and between 2,645 and 3,912 identified with CRCin the first round of the program.