The paper presents two wall-treatments employed with the standard k-ε turbulence model together with their consequences on the estimation of the flow characteristics (separation zone, velocity distribution, adverse/favourable pressure gradient, wall shear stress) and simulation resources (time and computational power). The two wall-treatments were developed by Manhart (2008) and Duprat (2010). The results are compared to those obtained with the standard k-ε turbulence model and the k-ω SST turbulence model, using the numerical computation software Code_Saturne CFD. The test case considered for the numerical simulations is a 3D diffuser geometry with water as fluid which undergoes flow separation. The results show that the two wall-treatments lead to an improvement of the accuracy in the prediction of the separation zone. The required time and computational power are improved, compared to the k-ω SST turbulence model.