The purpose of this work was to investigate the influence of the presence of the body in helmet oblique impacts on the tissue level response of the human head. The kinematic field of the head obtained from full-body and detached-head oblique impacts were used to drive a validated Finite Element model of the human head and evaluate predictors of the diffuse axonal injury (Von Mises stress in the brain) and subdural haematoma (internal energy of the Cerebro-Spinal Fluid (CSF)). It was found that the presence of the body considerably influences the intracranial response. To take into account this effect in detached-head impacts, inertial properties of the head were modified. When the head mass was increased, the Von Mises stress in the brain and the internal energy of the CSF decreased for impacts with relatively high tangential velocities. Modifying the head inertia matrix lowered the Von Mises stress in the brain and the internal energy of the CSF. The best correlation between the modified detached-head and full-body impact results was found when both the head mass and its inertia matrix were modified.