ABSTRACTThe electronic structures of actinide solid systems are calculated using the self-interaction corrected local spin density approximation. Within this scheme the 5f electron manifold is considered to consist of both localized and delo-calized states, and by varying their relative proportions the energetically most favourable (ground state) configuration can be established. Specifically, we discuss elemental Pu in its δ-phase, and the effects of adding O to PuO2.