The three-dimensional dynamics of shallow vortex dipoles is investigated by means of an innovative three-dimensional, three-component (3D-3C) scanning PIV technique. In particular, the three-dimensional structure of a frontal spanwise vortex is characterized. The technique allows the computation of the three-dimensional pressure field and the planar (x, y) distribution of the wall shear stress, which are not available using standard 2D PIV measurements. The influence of such a complex vortex structure on mass transport is discussed in the context of the available pressure and wall shear stress fields