Abstract : The study presented in this paper deals with the diagnostic evaluation of a system being implemented. The tested system's particularity is to provide a filtering process taken into user's account personal characteristics. The aim of diagnostic evaluation is to choose one filtering process between 8 proposed ones. 16300 interrogations are used as a representative sample. It combines characteristics relating to: the user's profile, the user's need of information and the filtering process. Answers are compared relating to: the number of common documents, the rank of common documents and the specificity degree of the query. These criteria give indication about the filtering impact.