The selection of a design wave is best obtained by the use of a relationship showing the construction costversusthe anticipated damage cost. In the present paper, the influence of the main parameters affecting the optimum design criteria has been studied in reference to practical cases.Indeed, this criteria has been applied to three different wave conditions obtained from a wave climate study conducted by the Hydraulics Division of the National Research Council of Canada in the Gulf of St. Lawrence. The damages were evaluated using results from breakwater scale models carried out in the Hydraulics Laboratory of Laval University. Three different types of armour units have been considered: that is, quarry stones, tetrapods, and ‘dolosse’.For the sake of comparison, we have studied, in addition to the three wave conditions and the three types of armour units mentioned above, the influence of the economic losses due to malfunction of the structure and of the choice of an annual interest rate. We have also taken into account the water depth at the structure, a parameter which was found often to play an important role in limiting the value of the design wave.