AbstractIntroductionQuitlines are standard care for smoking cessation; however, retaining clients in services is a problem. Little is known about factors that may predict dropout.AimsTo examine predictors of retention while in-program and at follow-up for clients enrolling in a state quitline.MethodsThis was a retrospective analysis of quitline enrolled clients from 2011 to 2017 (N = 49,347). Client retention in-program was categorized as (a) low adherence to treatment (receiving zero coaching calls), moderate (1–2 calls), and high adherence (3+ calls). Dropout at follow-up included participants who were not reached for the 7-month follow-up.ResultsMore than half the sample dropped out during treatment; 61% were not reached for follow-up. Women (odds ratio (OR) = 1.21; 95% confidence interval (CI) = [1.16, 127]) and those with high levels of nicotine dependence (OR = 1.03; 95% CI = [1.02, 1.04]) were more likely to have moderate adherence to treatment (1–2 coaching calls). Dropout at follow-up was more likely among clients who used nicotine replacement therapy (OR = 1.14; 95% CI = [1.09, 1.19]) and less likely among those who had high treatment adherence (OR = 0.41; 95% CI = [0.39, 0.42]).ConclusionGiven the relapsing nature of tobacco use and the harms related to tobacco use, quitlines can improve their impact by offering tailored services to enhance client engagement and retention in-treatment and at follow-up.