Objectives: This study focuses on the effectiveness of a five-day target youth smoking cessation program in terms of smoking behavior, psychological characteristics, physiological changes, and 1-month maintenance of non-smoking. Methods: The participants in this one-group pre-posttest study were 91 youth smokers registered to a smoking cessation school at a hospital in Seoul. Data analyses performed include descriptive statistics, x2-test, paired t-test, and ANOVA. Results: A five-day smoking cessation program significantly decreased expired carbon monoxide level, stress, and depression. In post-intervention urine test, urine cotinine was detected in 14 of 91 participants(15.4%). In a one-month follow-up telephone survey 80.2% responded maintaining non-smoking. Conclusion: This study demonstrated the effect of a five-day smoking cessation program for adolescent smokers.