Total variation (TV) minimization has become an important tool for the sparse image reconstruction. In this study a realistic 3D digital breast tomosynthesis (DBT) data was reconstructed and compared using two different forms of TV: (i) 2D reconstruction by applying TV layer by layer (ii) 3D reconstruction of the entire data. It can be assumed that a 3D reconstruction should perform better. However, in real DBT the resolution in z direction is about 10-15 times lower than the resolution in x-y plane. This study investigates the performance of the reconstruction when a TV term in z direction is added into the cost function of TV minimization.