Radar remote sensing is a tool of increasing importance in the study of volcanic sites. Synthetic aperture radar (SAR) is a high-resolution imaging tool used to survey areas which are not practical or safe to be directly inspected. With the introduction of the across-track SAR interferometry (IFSAR) technique, digital elevation models (DEM) can be produced. The usefulness of such interferometric products depends on the ability to extract information that can be used for geological interpretation. We analyzed the shuttle imaging radar C (SIR-C)/X-SAR multifrequency multipass interferometry mission over Mount Etna, Sicily, and we performed a supervised geological interpretation of the coherence maps and a fractal-based analysis of the IFSAR DEMs. The first permits us to recognize different volcanic terrain and to distinguish between vegetated and unvegetated areas, while the second allows us to validate the IFSAR DEMs and to detect large-scale geological features. This latter analysis, performed over the photogrammetric DEM, enabled us to recognize artifacts caused by digitizing and resampling. Obviously, IFSAR DEMs are not affected by these problems. As a consequence, IFSAR products are a valuable aid in geological interpretation.