Plasma measurements in the tails of Venus showed the existence of several ion populations. Measurements performed on Venera and Pioneer Venus spacecraft at different planetocentric distances showed the evolution of the plasma parameters along the tail. Low-energy ion fluxes measured in the tail at close downstream distances, are also observed farther downstream, and show low acceleration from 0.5 R v to 12 R v . High energy ions (energetic O + ions) reported from PVO observations in the tail at 10-12 R v seem to be the same ion component that was observed as energetic ions at the tail boundary close to the planet have on Venera spacecraft. We give evidences that these ions are accelerated in the narrow shear layer near the tail boundary.