Background: To explore how individuals reason when they make decisions about participating in colorectal cancer(CRC) screening.

Methods: Individuals randomized colorectal cancer (CRC) screeningto FIT or colonoscopy included in the Screening of Swedish Colons (SCREESCO) program was invited to focus group discussions and individual telephone interviews. The concept of shared decision-making (SDM: information; values/preferences; involvement) was used as a matrixfor the analyses. To validate findings, additional focus group discussions using the nominal group technique were performed.

Results: Lack of knowledge of CRC and CRC screening was prominent for participants and non-participants, while the results differed between the groups in relation to their values and preferences. The influence of significant others promoted participation while it prevented it among non-participants. Those who participated and those who did not made it clear that there was no need to involve health care professionals when making the decision.

Conclusions: Based on the results, a display of different ways to spread knowledge and communicate about CRC and CRC-screening could be applied such as, community-based information campaigns, decisions aids, interactive questionnaires, chat-functions and telephone support. The disparity in values and pref-erences between participants and non-participants may be the key to understand why non-participants make theirdecisions not to participate and warrant further exploration.