Porous RuO 2 /Ti electrodes were prepared from RuO 2 -La 2 O 3 /Ti (Ru:La = 7:3) electrodes with the complete dissolution of lanthanum ions in H 2 SO 4 . Although the voltammetric charge of RuO 2 -La 2 O 3 /Ti (Ru:La = 7:3) electrodes partially decreased as lanthanum ions were dissolved, charges of the resulting porous RuO 2 /Ti electrodes were still about 20 times as large as those of the conventional RuO 2 /Ti electrodes prepared by the thermal decomposition method. The novel route through RuO 2 -La 2 O 3 /Ti electrodes was significant for the preparation of porous RuO 2 /Ti electrodes.