Mindfulness training (MT) is an emerging therapeutic modality for addictive disorders. Nonjudgment of inner experience, a component of mindfulness, may influence addiction treatment response. To test whether this component influences smoking cessation, tobacco smokers (n = 85) in a randomized control trial of MT vs. Freedom from Smoking (FFS), a standard cognitive-behaviorally-oriented treatment, were divided into split-half subgroups based on baseline Five Facet Mindfulness Questionnaire nonjudgment subscale. Smokers who rarely judge inner experience (nonjudgment > 30.5) smoked less during follow-up when randomized to MT (3.9 cigs/d) vs. FFS (11.1 cigs/d), p < .01. Measuring trait nonjudgment may help personalize treatment assignments, improving outcomes.