SnO2 filled mesoporous tin phosphate was prepared by impregnating an Sn melt into the mesopores of hexagonal mesoporous tin phosphate with a pore size of 3 nm at 300 degrees C under vacuum. Although Sn was oxidized to SnO2 via a reaction with the oxygen ions consisting of one of tin phosphate pore wall frameworks at 300 degrees C, the pore wall material remained amorphous without showing any other phases. The electrochemical results revealed significant improvement of the reversible capacity to 805 from 400 mAh/g after the mesopores were filled with SnO2. This was because the SnO2 not only added capacity but also decreased high BET surface area of the mesoporous tin phosphate that caused the large irreversible capacity. (c) 2006 The Electrochemical Society.