TiO 2 (30–80wt.%) and ZrO 2 (48–75wt.%) were inserted inside the pores of SBA-15 mesostructured silica host by chemical solution decomposition (CSD) or internal hydrolysis (IH) of the corresponding alkoxides. Both methods yielded composites with 85–94% TiO 2 crystallinity (anatase). In case of ZrO 2 , CSD yielded >95% crystallinity (tetragonal phase), while IH gave an amorphous ZrO x -phase that does not crystallize up to 1073K. The guest Ti(Zr)-oxide phases did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of TiO 2 /SBA-15 and ZrO 2 /SBA-15 (CSD) composites up to 1073K did not change the nanocrystals structure and slightly increased the domain size derived from XRD data from 5.0–8.5 to 6–10nm for TiO 2 (IH and CSD) and from 4.5 to 6.5nm for ZrO 2 (CSD). After the same treatment the crystals domain size of bulk reference TiO 2 increased to >100nm with full conversion to rutile polymorph and of reference bulk ZrO 2 ––to 20–25nm with partial conversion to monoclinic modification. Thorough characterization of the texture, structure, location and dispersion by HRTEM, SAXS, EDS, SEM, XRD, N 2 -adsorption methods allowed evaluation of the assembling mode of TiO 2 and ZrO 2 inside SBA-15 nanotubes: amorphous layer, ensemble of small 4–5nm crystals (TiO 2 -IH and ZrO 2 -CSD) or single large 8.5nm crystals (TiO 2 -CSD).