Abstract Background: The COVID-19 pandemic has disrupted healthcare delivery, which is widely discussed as the distraction effect. This study aimed to estimate the distraction effect of the COVID-19 pandemic in Korea by analyzing colorectal and gastric cancer screening rates in the years 2019 and 2020. Methods: Information of eligible population who had colorectal and gastric cancer screening provided by the National Cancer Screening Program in the years 2019 and 2020 was collected. Participation rates were analyzed by age group, sex, geographic region, and calendar month. Percentage change was calculated by dividing the percentage point difference by the screening rate of the reference period (2019). Results: Overall, the colorectal and gastric cancer screening rates had decreased in 2020, compared to the reference period. For colorectal cancer, the screening rate decreased from 68.3% in 2019 (5,886,319 participants/14,526,424 eligible population) to 54.6% in 2020 (5,135,218/9,410,525) For gastric cancer, the screening rates decreased from 61.9% in 2019 (7,194,489/11,625,627) to 54.6% in 2020 (6,244,491/11,439,246). In March, during the first wave, the screening rates declined sharply (percentage change: colorectal, 56.6%; gastric, 57.3%). Although the screening rates had rebounded aftermath, they declined again in December, during the third wave (percentage change: colorectal, 17.0%; gastric, 13.8%). According to specific-age group, we found a substantial decline in screening rates for older adults aged 80~84, and those over 85 (percentage change: colorectal, 19.0% & 23.0%; gastric, 17.4% & 25.1% respectively). Conclusion: During the COVID-19 pandemic, the screening rates for both colorectal and gastric cancer decreased. There was a substantial decline during the first and the third waves of the epidemic, in March and in December. The older adults group showed the highest reduction in screening rates. However, comparing the screening rate by region and sex, we did not find a significant difference. Delayed cancer diagnosis or excess death due to distraction effect of the COVID-19 pandemic has not yet been detected in Korea, therefore, further studies are needed. Citation Format: Seung Hee Seo, Hyeree Park, Jong Heon Park, Bhumsuk Keam, Shin Hye Yoo, Aesun Shin. Colorectal and gastric cancer screening rates in Korea during the COVID-19 pandemic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 433.