['To estimate the causal effects of online community use on 30-day point prevalence abstinence at 3 months among smokers that received a combined Internet/phone intervention for smoking cessation.', 'Participants were 399 adult smokers selected from the combined Internet/phone arm of The iQUITT Study (Graham et al., 2011), a randomized trial of Internet and proactive telephone counseling for smoking cessation. All selected participants had accessed a web-based smoking-cessation program with an established online community and received at least one telephone counseling call. Automated tracking metrics of passive (e.g., reading posts, viewing profiles) and active (e.g., writing posts, sending messages) community use were extracted at 3 months. Self-selected community use defined the groups of interest as None, Passive, and Both (passive and active). Inverse probability of treatment weighting corrected for baseline imbalances on demographic, smoking, and psychosocial variables. Propensity weights estimated via generalized boosted models were used to calculate average treatment effects (ATE) and average treatment effects on the treated (ATT).', 'Patterns of community use were None = 145 (36.3%), Passive = 82 (20.6%), and Both = 172 (43.1%). ATE-weighted abstinence rates were None = 12.2% (95% CI = 6.7-17.7), Passive = 25.2% (95% CI = 15.1-35.2), and Both = 35.5% (95% CI = 28.1-42.9). ATT-weighted abstinence rates indicated even greater benefits of passive community use by nonusers.'] Does online community use predict abstinence in combined Internet/phone intervention for smoking cessation?