In this work we use density functional theory (DFT) to investigate the influence of semi-local exchange and correlation effects on the electronic and optical properties of zinc oxide. We find that the inclusion of such effects using the Tran-Blaha modified Becke-Johnson potential yields an excellent description of the electronic structure of this material giving energy band gap which is systematically larger than the one obtained with standard local functionals such as the generalized gradient approximation. The discrepancy between the experimental and theoretical band gaps is then significantly reduced at a computational low cost. We also calculated the dielectric functions of ZnO and find a violet shift to the absorption edge which is in good agreement with experimental results. * jailton almeida@hotmail.comRecently proposed Tran-Blaha modified version of the Becke-Johnson potential (TB-mBJ) [20] has proved to be a successful method for accurate band gaps of semiconductors and insulators [21][22][23][24][25]. Furthermore, it has a computational cost as the LDA or GGA. For ZnO, it has been shown to lead to band gaps close to the experimental values [8,24,25].In this work, we use the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential [20] to investigate the electronic structure and optical response of ZnO. We found that TB-mBJ potential greatly improves the description of the electronic structure of ZnO compared to GGA, but still has several drawbacks with respect to GW calculations.