Abstract Introduction Little experimental research has evaluated whether the effects of cigarette package inserts with efficacy messages and/or pictorial health warning labels (PHWLs) differ across key subgroups of adults who smoke. Methods Adults who reported currently smoking (n=367) were randomly assigned to one of four groups: small text-only health warning labels (HWLs) on pack sides (control); inserts with efficacy messages and small HWLs (inserts-only); PHWLs showing harms of smoking (PHWLs-only); both (inserts+PHWLs). Participants received a 14-day supply of cigarettes labeled to reflect their group. Every evening over two weeks, participants reported forgoing and stubbing out cigarettes before they finished smoking over the prior 24 hours, combined into a binary indicator of either behavior (e.g., forgoing/stubbing). Separate mixed-effects logistic models were estimated to evaluate moderation of labeling group contrasts (i.e., PHWLs vs not; inserts vs. not; inserts-only vs. inserts+PHWLs; PHWLs-only vs. inserts+PHWLs) by baseline covariates (self-efficacy to quit, intention to quit, education, health literacy, time discounting), predicting day-level forgoing/stubbing. Results Education moderated PHWL effects, with PHWLs predicting more forgoing/stubbing only among those with low education (OR=4.68, p<0.001). Time discounting moderated insert effects, with inserts promoting fogoing/stubbing only among those with low time discounting (i.e., lower impulsivity; OR=4.35, p<0.001). Conclusions Inserts with efficacy messages appear effective mostly among people with low time discounting, whereas PHWLs appear most effective amongst those with low education, suggesting their potential to address education-related disparities. Labeling strategies appeared equally effective across subgroups defined by self-efficacy to quit, quit intention, and health literacy. Combining inserts with PHWLs did not appear to mitigate moderation effects. Implications This randomized trial with adults who smoke suggests that cigarette packs with inserts describing cessation benefits and tips can promote cessation-related behaviors (i.e., forgoing or stubbing out cigarettes) among those with low time discounting (i.e., low impulsivity). Alternative interventions may be needed for people with high time discounting, as found in cessation trials. Pictorial health warning labels (PHWLs) appear most effective among those with low education, potentially addressing education-related disparities. No differential effects were found for those with different levels of self-efficacy to quit, quit intentions, or health literacy. Combining inserts and PHWLs may not be more effective than either alone.