The major goal of cancer screening programs is the reduction of disease-specific mortality by detecting malignant tumors in an early and still curable stage. Sensitive screening tests are used in apparently healthy people and conspicuous findings are referred for further investigations. Taking the personal disease risk into account, persons considering participation in a screening program should be informed about the methods, benefits and disadvantages of the screening program. This information, together with personal preferences, is the basis for a well-informed decision for or against participation in a screening program. This article imparts essential knowledge that is needed for individual medical counseling on screening for colorectal, skin, breast and prostate cancer.