The structure of an upward wall-bounded bubbly flow is investigated in the simple case of a turbulent boundary layer developing on a vertical flat plate. The data reported is part of a research program currently under progress. They concern the void fraction distribution, the wall shear stress, and the mean liquid velocity profiles. It is shown that depending on their mean diameter, a significant fraction of the bubbles deflected towards the wall. This migration, together with a significant deceleration of the bubbles at the surface, prove to be the two main mechanisms responsible for the so-called void peaking phenomenon. Besides, the skin friction coefficient which depends both on the amplitude of the peak, and on the free-stream velocity is found to increase in the presence of the dispersed phase. This increase is linked to a modification of the universal logarithmic law of the wall, and to a depression of the wake.