We study the rheology of a sheared 2D suspension of non-Brownian disks in presence of walls. Although, it is of course possible today with modern computers and powerful algorithms to perform direct numerical simulations that fully account for multiparticle 3D interactions in the presence of walls, the analysis of the simple case of a 2D suspension, provides valuable insights and helps to understand 3D results. Thanks to the direct visualization of the whole 2D flow (the shear plane), we are able to give a clear interpretation of the full hydrodynamics of semi-dilute confined suspensions. For instance, we examine the role of particle-wall and particle-particle interactions to determine the effective viscosity of confined sheared suspensions. We provide numerical estimates of the intrinsic viscosity [η] as well as of the contribution of hydrodynamic interactions β to the effective viscosity for a wide range of confinements. As a benchmark for our simulations, we compare the numerical results obtained for [η] and β for very weak confinements with analytical values [η]∞ and β∞ obtained for an infinite fluid. If the value [η]∞ = 2 is well known in the literature, much less is published on β value. Here, we analytically calculate with a very high precision β∞ = 3.6. Finally, we reexamine the 3D case in the light of our 2D results. * philippe.peyla@univ-grenoble-alpes.fr 2