Modeling techniques and the decision process for research question definition using PICO (Population, Intervention, Control/Comperator, Outcome) in HTA (Health Technology Assessment) problems are described briefly in the first part of the paper. The second part deals with some aspects of realized screening questions regarding cost effectiveness of organized breast cancer screening in Austria and a screening program for abdominal aortic aneurysm. In case of breast cancer a closer look on model calibration for natural history behavior of tumor growth/development is given.