We present a theory for analyzing the effects of chain stiffness on the diffusion-influenced quenching kinetics of an excited polymer. We model the polymer as an optimized Rouse-Zimm chain and the quencher molecule as a spherical particle. The excitation is considered to be localized at any one monomer, or to move randomly along the chain backbone. In regard to the dependence on the chain stiffness, we found two distinctive kinetic regimes. When the excitation migration rate is small, the quenching rate decreases as the chain becomes stiffer. On the other hand, when the mobility of excitation is large, the opposite trend is observed. We also investigate the dependence of Stern-Volmer coefficient on the length and stiffness of the chain in the fast excitation migration limit. (C) 2003 American Institute of Physics.