It has become common-place for clients to question program evaluation’s primary function: its ability to produce judgments that lead to relevant recom mendations. Some well-known authors have formulated hypotheses in an attempt to explain this situation; however, these hypotheses have not been supported by empirical research as yet. The present research carries out a breakthrough in this direction by having as objective to validate these explanations. For that purpose, it must have an operational representation of the process specific to program evaluation in order to describe the practice. Hurteau and Houle (2005) propose such a representation – modeling – which is based on various theoretical contributions, of which that of Scriven (1980) which introduced the concept of “logic of evaluation” and those of other authors (Hurteau, 1991; Fournier, 1995; Stake, 2004). The present study presents the modeling as well as the results of its validation.