Long-term, real-world data, as opposed to academic or research data, on outcomes of smoking cessation clinics are scarce. We assessed patient outcomes over a 10-year period at a smoking cessation clinic in a community teaching hospital in Japan and explored predictors of successful smoking cessation. We used data from a prospective registry of cigarette smokers who participated in a 3-month smoking cessation program comprising combined pharmacological treatment and cognitive behavioral therapy and explored factors associated with program execution and successful smoking cessation. The primary outcome was smoking cessation, defined by quitting completely between the 8-week and 12-week sessions, with verification according to exhaled carbon monoxide (CO) level of ≤10 ppm. Between August 2007 and December 2017, 813 patients with nicotine dependence participated in the program. The number of participants decreased after Japan׳s 2010 tobacco tax increase. Among participants, 433 (53.3%) completed the program. In multivariate analysis, the number of cigarettes smoked daily (odds ratio [OR] 0.98, 95% confidence interval [CI] 0.96, 0.99), cardiovascular disease (OR 1.75, 95% CI 1.16, 2.68), chronic obstructive pulmonary disease (OR 1.74, 95% CI 1.10, 2.78), and gastric/duodenal ulcer (OR 1.77, 95% CI 1.04, 3.08) were significantly associated with program completion. Among program completers, 288 (66.5%) achieved smoking cessation. Exhaled CO level (OR 0.94, 95% CI 0.93, 0.97) and mental disorders (OR 0.53, 95% CI 0.33, 0.85) were negatively associated with successful smoking cessation. Baseline exhaled CO level and mental disorders were significantly associated with either success or failure of smoking cessation.