Background: The decision of prescribing bronchodilators cannot be empirically justified until a specific diagnosis is made.  Additional Investigations should be used in cases where spirometry is contraindicated or PFT findings are inconclusive chronic dyspnea is a frequent observation in medical practice. It is defined as shortness of breath lasting longer than one month.  Spirometry for pulmonary function testing (PFT) provides a stepwise algorithmic approach to establish an accurate diagnosis for the cause and is of great help in preventing over–diagnosis or under–diagnosis of common respiratory diseases. The aim of the present study was to study the role of spirometry in evaluating patients of chronic dyspnea and to classify findings into obstructive/restrictive/mixed patterns.  To further analyze the study population categorized by age groups and sex based on various spirometric variables, make a specific diagnosis and then study the pattern and bronchodilator response in cases. Methods: 200 adult patients, who visited the T.B. and Chest OPD of RIMS, Ranchi with features of chronic dyspnea, were included in the study. A detailed clinical history, clinical examination and spirometry were done in all patients included.  A repeat Post–bronchodilator spirometry was performed in those showing an abnormal pattern. Study population was categorized into three age groups and frequency of male/female noted.   Obstructive/restrictive/mixed patterns were identified in different age groups and specific diagnosis was made using additional investigations where required. Response to bronchodilator was recorded. Overall pattern, distribution and disease association with age was studied. Results: Most symptomatic patients including both sexes were in the middle age group (56 males & 38 females), followed by older (>60yrs) age group (72 males vs 20 females). 66.5% Subjects whose spirometric findings were abnormal were subjected to a post–bronchodilator spirometry. There was a statistically significant improvement (p<0.05) in the lung volumes (FEV1 %, FEV3 %), forced vital capacity (FVC %) and expiratory flow (FEF25–75 %) after bronchodilator administration. Obstructive pattern was more frequent in middle age group (39/75) whereas a restrictive pathology was commoner in older age group (20/33).  COPD (45) & Asthma (44) were the most common specific diagnosis. Restrictive lung disease due to Lung parenchymal damage (21) and Pleural and chest wall deformity (13) was frequently observed in older subjects. Conclusion: Pulmonary function testing by Spirometry must be performed in all possible cases to classify the etiology and make a specific diagnosis of common clinical conditions like Asthma or COPD. Not all symptomatic cases show spirometric abnormalities. Prevalence of Obstructive lung disease is higher in middle age group whereas Restrictive lung disorders increase with increasing age