In this Letter, we study the effect of external noise (EN) on the intrinsic stochastic reaction rate oscillations (RRO) in CO oxidation on nm-sized Pd particles. It is found the optimal RRO can be enhanced by appropriate EN and, moreover, there is an optimal EN by which the optimal RRO can be most highly enhanced. This result shows EN may play a constructive role in the intrinsic stochastic reaction oscillations via the interplay with internal noise, and the oscillations can selectively employ the EN to reach a best oscillatory performance. Therefore, EN should be paid high attention in the study of the kinetics in CO oxidation on nm-sized Pd particles. (c) 2008 Elsevier B.V. All rights reserved.