Introduction:Quitline is well recognized as one of important tobacco control resources. Evaluating the effectiveness of a Quitline is a crucial concern for its stakeholders. The project of "Evaluation and Monitoring for Taiwan Smokers' Helpline (TSH)" has been funded by the Health Promotion Administration, Taiwan. The external monitoring processes followed the principle of the "INPUT-PROCESS-OUTPUT" model to evaluate the TSH's performance. Objectives:To evaluate the TSH’s required responsibilities which include professionalism, service quality, and outcomes of smoking cessation counseling. Methods:Quality guidelines that were issued by the US Centers of Disease Control and Prevention (CDC) were used as the gold standards to check against performance of the Taiwan Smokers' Helpline. The study used datasets provided by the TSH and a series of telephone surveys to assess smoking rate changes of those who received the TSH’s counseling services. Results:The TSH provided services for a total of 16249 callers in 2019, including 8614 counseling services, and 3379 (39.2%) multi-section proactive counseling services. In the follow-up surveys, 6-month point abstinence rate was 20.1% (intention-to-treat rate) ~41.6% (response rate), and 6-month continuous abstinence rate was 15.7% (ITT rate) ~32.6% (response rate). The overall satisfaction rate of TSH services was 97.5%. For other indicators, 91.4% incoming calls were promptly answered, 95.8% calls were answered in 30 seconds, messages response rate within 24 hours was 100%, and the TSH’s net telephone line occupying rate was 31.2%. In the OUTPUT aspect, the incoming calls volume was decreased from 9180 during the first 9 months in 2018 to 8822 in the same period of 2019. Conclusion(s):The TSH’s performance was generally satisfactory; however, it also faces an emerging crisis in losing incoming calls. The external evaluation team has delineated the causes and trend of diminishing incoming calls and made an international comparison by reviewing existing literature.