OBJECTIVES: Disinvestment decisions are made when existing health technologies do not fulfil criteria such as efficacy, effectiveness or safety. Breast cancer screening (BCS) using mammography is widely implemented; yet many studies show that a significant percentage of women are overdiagnosed and overtreated. The objective of this study is to analyse the effects of a BCS disinvestment decision in Asia-Pacific countries, and to explain any differences between countries.  METHODS: A mathematical model was developed to analyse population outcomes and costs associated with breast cancer (BC) from 2014 to 2050 in Australia and Korea. Population outcomes were measured as number of women diagnosed with BC, number of women overdiagnosed and number of deaths associated with BC. The model allowed the analysis of these outcomes with and without a BCS programme in place, as a proxy to evaluate the effects of disinvestment.   RESULTS: Results varied between countries, particularly depending on ethnicity and level of participation in the BCS programme. The model predicted a significant increase in the number of deaths associated with BC in Korea; a disinvestment decision, however, would not have a large impact on the number of deaths, due to currently high levels of overdiagnosis, and overall costs would be significantly reduced. A disinvestment decision in Australia would dramatically reduce the number of overdiagnosed women, although mortality due to BC would be higher.  CONCLUSIONS: This analysis has shown that the cost-effectiveness of BCS programmes should be evaluated over the long-term in order to take into account the consequence of overdiagnosis. Disinvestment decisions are complex and must be made locally, taking into consideration specific characteristics of the population under study.