This study sought to evaluate whether individual differences in the reinforcing value of smoking relative to physical activity (RRVS) moderated the effects of physical activity on smoking abstinence symptoms in young adult smokers. The repeated-measures within-subjects design included daily smokers (N = 79) 18–26 years old. RRVS was measured with a validated behavioral choice task. On 2 subsequent visits, participants completed self-report measures of craving, withdrawal, mood, and affective valence before and after they engaged in passive sitting or a bout of physical activity. RRVS did not moderate any effects of physical activity (ps > .05). Physical activity compared with passive sitting predicted decreased withdrawal symptoms, β = −5.23, 95% confidence interval (CI) [−6.93, −3.52] (p < .001), negative mood, β = −2.92, 95% CI [−4.13, −1.72] (p < .001), and urge to smoke. β = −7.13, 95% CI [−9.39, −4.86] (p < .001). Also, physical activity compared with passive sitting predicted increased positive affect, β = 3.08, 95% CI [1.87, 4.28] (p < .001) and pleasurable feelings, β = 1.07, 95% CI [0.58, 1.55] (p < .001), and greater time to first cigarette during the ad libitum smoking period, β = 211.76, 95% CI [32.54, 390.98] (p = .02). RRVS predicted higher levels of pleasurable feelings, β = 0.22, 95% CI [0.01, 0.43] (p = .045), increased odds of smoking versus remaining abstinent during the ad libitum smoking period, β = 0.04, 95% CI [0.01, 0.08] (p = .02), and reduced time to first cigarette, β = −163.00, 95% CI [−323.50, −2.49] (p = .047). Regardless of the RRVS, physical activity produced effects that may aid smoking cessation in young adult smokers. However, young adult smokers who have a higher RRVS will be less likely to choose to engage physical activity, especially when smoking is an alternative.