Background: Long-term cigarette smoking is a major risk factor for chronic respiratory diseases and progressive decline in lung function. Pulmonary function tests (PFTs) provide an objective assessment of airway obstruction and restrictive lung impairment.Objective: To evaluate pulmonary function abnormalities among long-term smokers and determine the association between smoking exposure and spirometric parameters.Methods: A retrospective observational study was conducted among 220 long-term smokers attending the pulmonary medicine outpatient department. Demographic details, smoking history, respiratory symptoms, and spirometry findings were analyzed. Pulmonary function parameters including forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), FEV₁/FVC ratio, and peak expiratory flow rate (PEFR) were evaluated.Results: Among 220 participants, 81.4% were males and 18.6% females. The mean smoking duration was 22.7 ± 8.5 years with an average smoking exposure of 31.4 ± 12.8 pack-years. Abnormal spirometry was observed in 71.8% of participants. Obstructive lung disease was detected in 58.2%, restrictive pattern in 9.1%, and mixed defects in 4.5%. Significant reductions in FEV₁ and FEV₁/FVC ratio were observed with increasing smoking duration.Conclusion: Long-term smoking is associated with significant deterioration in pulmonary function, predominantly producing obstructive ventilatory defects. Early spirometric screening and smoking cessation interventions are essential to prevent irreversible lung damage.