The aim of this paper is to present the results obtained with a 3-D numerical method allowing the prediction of the cavitation behaviour of a centrifugal pump and to compare this prediction to model tests. The proposed method consists in assuming the cavity interface as a free surface boundary of the computation domain and in computing the single phase flow. The unknown shape of the interface is predicted by an iterative procedure matching the cavity surface to a constant pressure boundary (pv). The originality of the presented method is that the adaptation process is done apart from the flow calculation, allowing to use any available code.