Introduction: Among the risk factors for squamous cell carcinoma of the head and neck, smoking is still the most important today. Several studies agree on the effect of smoking on tumor microenvironment, while the definition of former smokers and the time of smoking cessation on biologic effect differs among papers. Methods: We conducted a narrative review on smoking effects in HNSCC. Results: There is evidence that smoker patients have a poorer prognosis than never smokers and former smokers. Translational studies show a relationship between smoking status and gene expression and support the importance of smoking cessation, for instance, demonstrating an inverse relationship between tumor-infiltrating lymphocytes and smoking. Conclusion: Convincing data suggest that quitting smoking at any time may improve patient outcomes. We advocate smoking cessation also after cancer diagnosis.