In this work, the single ionization of helium atoms with the positive ions, H+, C6+ and U92+, as the incident projectiles, is studied in the high impact energy range. The fully differential cross sections are calculated using the four-body continuum-distorted-wave method, in both the prior- and post-forms. In these calculations, the correlated Silverman’s two-parameter wave function, as the ground state of helium atom, has been used. The inter-nuclear and post-collision effects have been included into the calculations in the prior- and post-forms, as a final integration and operator-type potential, respectively. Finally, the results of the present work have been compared, where possible, with other relevant experimental data and theoretical results, in terms of the different kinematical conditions of momentum transfer, ejected electron scattering angles and ejected electron energies.