Objective To compare the differences between residents who did and who did not participate in a community colorectal cancer screening based on the results of their colorectal colonoscopy and explore the reasons.

Methods The residents who underwent a colonoscopy in a central hospital in Shanghai from 2017 to 2020 were divided into two groups according to whether they had been screened in the community， and t test and χ² test were used to compare the results of the colonoscopy （detection of lesions） of the examinees with different ages， genders， whether they had a history of colorectal cancer， and whether they had been screened in the community. The correlation between whether they had participated in the community screening and the detection of lesions was analyzed by the logistic regression model.

Results From 2017 to 2020， the hospital had performed a colonoscopy for 6 389 people， and 3 623 lesions were detected， with a detection rate of 56.71%. There were 413 residents who had been screened in the community， accounting for 6.46% of the total number of those receiving a colonoscopy. 243 patients were found with pathological changes， with a detection rate of 58.84%. Compared with the residents who did not participate in the community screening， the proportion of adenoma and polyp was higher in those who had participated in the screening （χ²=50.44， P<0.001）. Among the residents without a history of colorectal cancer， the proportion of adenoma and polyp was higher in those who had participated in the community primary screening （χ²=51.86， P<0.001）. Among the residents who had not participated in the community screening， the proportion of residents with colorectal cancer history was higher （χ²=74.33， P<0.001）. Multivariate regression analysis showed that there was no correlation between participation in community screening and detection of any lesions by colonoscopy （OR=0.905， 95%CI： 0.734‒1.117） or detection of colorectal cancer related lesions （OR=1.113， 95%CI： 0.901‒1.375）.

Conclusion The proportion of residents who have participated in community screening among patients undergoing colonoscopy is low， but the asymptomatic population initially screened by the community and the symptomatic population not initially screened by the community are homogeneous， and the detection rate of precancerous lesions such as adenomas and polyps is high. It is suggested that local measures should be taken to improve residents' colonoscopy response rate， so as to obtain better screening benefits.