The modification of pre-sintered BaTiO3 grains (5–10m in size) by leaching under hydrothermal conditions was investigated using atomic absorption spectroscopy of the leaching solution and TEM methods including EELS for the modified particles. The results clearly indicate that it is possible to form leaching zones on the surface of BaTiO3 grains in a defined way by exploiting the thermodynamic instability of BaTiO3 in aqueous environment. The amount of Ba ions dissolved from the BaTiO3 seeds (up to 2 mol%) and, therefore, the thickness of the depletion layer (up to 15 nm) can be adjusted by variation of the leaching temperature, leaching time and/or the leaching medium. Depending