Introduction: Chronic obstructive pulmonary disease (COPD) is the third cause of mortality and it is smoking-related. It is characterized by a non-reversible airflow limitation and a progressive worsening of the respiratory function. Objective: The aim of this study is to point out the benefit of smoking cessation combined with a single inhaler triple therapy in terms of clinical and functional outcome in this setting. Methods: A retrospective analysis was performed in patients affected by severe COPD and at least one exacerbation a year, who underwent a smoking cessation program. All patients underwent a 6 min walking test, body plethysmography, and an exhaled test for carbon monoxide. The modified medical research council test (mMRC) test, the Fagestrom nicotine dependency test (FTND) and the COPD assessment test (CAT) questionnaire were also administered. All patients were checked at the baseline and in the six-month follow-up after the start of the treatment. Results: Smoking cessation was achieved by 51% of patients within a month and it was confirmed by eCO measure (<7 ppm). Patients who quit smoking reported better results after six months compared with patients who did not. The increase in FEV1 within the group of quitters was 90 mL (p < 0.05) and the walking test improved by 90 m (p < 0.01); eCO decreased by 15 ppm (p < 0.01) while FVC increased by 70 mL (p < 0.05). No significant changes were recorded within the group of sustainers. The difference in functional changes between groups was significant with regard to FEV1, cCO, and WT. Conclusions: Smoking cessation enhances the efficacy of single inhaler triple therapy, improving clinical and functional variables after six months from the start.