Objective: Smoking cessation treatment, which is now covered by insurance, is usually provided on an outpatient basis for approximately 3 months. It should ideally be evaluated not only by the rate of smoking cessation at the end of the treatment, but also by the length of the continuation of smoking cessation. However, as it is difficult to conduct long-term follow-up after the end of smoking cessation treatment, few studies have followed up successful cases of short-term smoking cessation for a long period in Japan.Methods: In this study, we examined the behaviors of nicotine-addicted patients who consulted our smoking cessation clinic, and investigated the current situation of long-term smoking cessation and involved factors.Results: The rate of smoking cessation at the end of the treatment was 71.8%. We found that 61.1%, 54.0%, and 50.6% of patients successfully quit smoking after the end of treatment for one, 2, and 3 years, respectively. However, 41.1% of male patients who succeeded restarted smoking within 6 months after the end of treatment.Conclusion: Additional support for patients who successfully quit smoking at an early stage at one year, or 6 months for males, is required to encourage them to continue to cease smoking.