Objective: Routine, population-based mammographic screening for breast cancer has been implemented nationally in Japan for the past decade. The objective of this study was to evaluate the knowledge of the general public and of nurses concerning breast screening practices in Japan, especially with regards to the benefits and risks of breast cancer screening.

Methods: In 2014, a questionnaire regarding the benefits and risks of breast cancer screening was administered to women who underwent breast cancer screening and to registered nurses. The questionnaire was distributed to 1,649 women and 1,905 registered nurses.

Results: Completed questionnaires were returned by 1,552 (94.1%) of the screened participants and 1,710 (89.8%) nurses. The majority of the screened participants and registered nurses believed that screening prevented or reduced the risk of developing breast cancer (86% and 62%, respectively); that screening reduced the mortality risk of breast cancer by more than 50% (69% and 60%, respectively); and that 10 years of regular screening for 50-year-old women could prevent ≥ 10 breast cancer deaths per 1,000 women (62% and 61%, respectively).

Conclusions: Women in the target population and registered nurses were aware that earlier diagnosis led to better prognosis, but demonstrated misconceptions regarding other aspects of the benefits and risks of breast cancer screening. In Japan, all women should be educated on both the benefits and risks of breast cancer screening to enable them to make an informed decision on whether to participate in the mammographic breast cancer screening program.