Evaluated intrinsic-extrinsic model of motivation for smoking cessation using two samples (Ns=1,217 and 151) of smokers. Analysis on Reasons for Quitting scale supported intrinsic-extrinsic motivation distinction, defining four-factor model with two intrinsic and two extrinsic dimensions. Found that smokers with higher levels of intrinsic relative to extrinsic motivation were more likely to achieve abstinence from smoking. (Author/NB)