Carbon nanotubes (CNTs) with external and internal decoration of Fe2O3 nanoparticles (NPs) were imaged by scanning transmission X-ray microscopy (STXM) with a concurrent identification of the electronic structure. For Fe2O3 outside CNTs, a carbon coating on CNTs was observed while for Fe2O3 inside CNTs, pure CNTs without carbon coating could be clearly identified. Surface oxidation of CNTs with internal decoration of Fe2O3 NPs was also found which showed a heterogeneous distribution. Further experiments suggest that the oxidization of CNTs may favor the internal Fe2O3 decoration of CNTs. (C) 2013 Elsevier B.V. All rights reserved.