The paper presents the use of computerized diagnostic decision support systems for medical diagnostics in medicine. The structure of classical decision tree and the advantages and disadvantages of using classification trees have been discussed. Moreover, the paper deals with the effect of classification trees with respect to other classic statistical methods, such as discriminant analysis and logistic regression, taking into account the problem of multicollinearity of variables and the problem of the occurrence of the so-called missing data. Additionally some examples of the application of classification trees in medicine have been shown.