The effect of lanthanide ions such as La3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, Yb3+ and Y3+, On the electrodeposition of cobalt oxyhydroxide (CoOOH) and manganese oxide (MnO2) was investigated. All the Ianthanide ions suppressed the electrodeposition of these compounds. The suppression effect was much stronger for the electrodeposition of CoOOH than for that of MnO2, and the amount of the incorporated lanthanide ion in the deposited film was higher for the former than for the latter, In the electrodeposition of CoOOH, the suppression effect increased with increasing amount of incorporated lanthanide ion in the deposited film in the order Yb3+ > Y3+ > Dy3+ > Gd3+ greater than or equal to Sm(3+)greater than or equal to Nd3+ > Pr3+ > La3+. This order is almost the same as that of the decrease in the ionic radius. However, no clear dependence of the suppression effect on the type of lanthanide ion was observed for the electrodeposition of MnO2. It is assumed that the lanthanide ion is intercalated in the Co-O layer of the CoOOH structure, but is only attached to the surface of the MnO2 during the electrodeposition. The relationship between the suppression effect and the state of incorporation of the lanthanide ion is discussed.