Objective CT-colonography has been suggested to be less burdensome for primary colorectal cancer (CRC) screening than colonoscopy. To compare the expected and perceived burden of both in a randomised trial. Design 8844 Dutch citizens aged 50-74 years were randomly invited for CRC screening with colonoscopy (n=5924) or CT-colonography (n=2920). Colonoscopy was performed after full colon lavage, or CT-colonography after limited bowel preparation (noncathartic). All invitees were asked to complete the expected burden questionnaire before the procedure. All participants were invited to complete the perceived burden questionnaire 14 days later. Mean scores were calculated on 5-point scales. Results Expected burden: 2111 (36%) colonoscopy and 1199 (41%) CT-colonography invitees completed the expected burden questionnaire. Colonoscopy invitees expected the bowel preparation and screening procedure to be more burdensome than CT-colonography invitees: mean scores 3.0 +/- 1.1 vs 2.3 +/- 0.9 (p < 0.001) and 3.1 +/- 1.1 vs 2.2 +/- 0.9 (p < 0.001). Perceived burden: 1009/1276 (79%) colonoscopy and 801/982 (82%) CT-colonography participants completed the perceived burden questionnaire. The Conclusion In a CRC screening programme, colonoscopy invitees expected the screening procedure and bowel preparation to be more burdensome than CTcolonography invitees. In participants, CT-colonography was scored as more burdensome than colonoscopy. Intended participation in a next screening round was comparable.