In recent years, increased attention has been given to guidelines for cost-effectiveness analysis of medical interventions, and some of these guidelines (such as NICE [1]) have become rather influential. In the paper, we present a model of retrieving and processing information to be used for the study of guidelines and their use. Our main result, which relies on a version of the theorem of Blackwell [2], shows that in cases where there are sufficiently many decisions to be made on the basis of the information obtained, there can be no other objective ranking of methods than the trivial one ranking more information is higher than less information. In our context, this means that guidelines may have administrative advantages but cannot be considered as a scientifically based approach to better decision making.