Recently developed cyclotrimethylene trinitramine (RDX)-based nanostructured explosive compositions were shown to exhibit greatly reduced initiation sensitivity as compared to conventional compositions prepared with coarser, micrometer-scale RDX. In particular, improvements were shown in the sensitivity towards shock and impact stimuli, key sources of inadvertent initiation. Such an improved response to mechanical stimuli is believed to be largely a result of smaller crystal and void sizes. Characterization of these structural parameters is therefore necessary in order to construct a meaningful physical description of these novel explosive compositions. Herein, we report the results of a detailed structural characterization of these novel RDX-based nanocomposites. The analyzed specimens were in pellet form with nominally 10% porosity. These results constitute an unprecedentedly complete structural picture of this new class of energetic materials.