Gallium nitride nanorods with a 15- 40 nm diameter and a 50-150 nm length have been synthesized in monodisperse spherical mesoporous silica particles (MSMSP) by high-temperature annealing the Ga2O3 precursor in ammonia. The template material (a-SiO2) was selectively removed by etching the composite MSMSP/GaN particles in HF. The individual GaN nanorods were thus obtained. It is shown, that the size of GaN nanorods was much higher than the pore size of MSMSP (diameter ~3 nm, length ~10 nm). The possible mechanism of formation of GaN nanorods was proposed. Redistribution of material inside the composite particles MSMSP/GaN possibly occurred by surface diffusion of gaseous molecules in mesopores and by diffusion of Ga and N atoms in a-SiO2.