It is a matter of debate whether, and if so, to what extent, cancer screening programs reduce all-cause mortality. Against this backdrop, we analyzed potential effects of several cancer screening approaches on all-cause mortality in two representative Western European populations.We used mortality data from the UK (England &Wales) and Germany from 2015 and published figures from screening studies on relative reduction in mortality for screened cancers to calculate the expected decline in all-cause mortality in these countries. We determined the required sample size for demonstrating a 3% reduction in all-cause mortality with a narrow (95%) confidence interval in a hypothetical screening trial.A relative 20% reduction in breast cancer mortality can be accompanied by a maximum 1.7-1.8% reduction in all-cause mortality in England & Wales and Germany, respectively. Expected declines are smaller for sigmoidoscopy screening (1.0-1.2%), prostate-specific antigen (PSA) screening (0.4-0.6%), and skin cancer screening (0.2%). To obtain a 95% confidence interval of +/-1% for demonstrating a 3% decline in all-cause mortality, a study size of 596 200 persons is required.Because the proportion of cancer deaths in all deaths in Western Europe is relatively low, cancer screening procedures can reduce all-cause mortality by only 1-3%. However, this reduction is relevant to public health.