Background: Obstructive Lung Diseases (OLDs), could lead to progressive hyperinflation of the lungs that cause increased work of breathing, impaired gas exchanges and functional limitations in patients. In this study, thoracic circumference of patients in upper and lower third were measured directly and the association of the upper to lower third width of chest with spirometric parameters was evaluated. Materials and Methods: In this cross-sectional study, five hundred twenty nine consecutive patients, with obstructive pattern in spirometry (FEV1/FEVC<70% and FEV1<80%), and 143 controls with normal spirometry were entered. Demographic and clinical data including age, sex, smoking, type, duration and severity of disease and spirometric characteristics were recorded. Upper Third circumference of Chest (UTCC) at axillary level, and Lower Third circumference of Chest (LTCC) at lower rib edge, were measured with an ordinary tape meter.Asthma Control Test (ACT) questionnaire for asthmatic and COPD Assessment Test (CAT) questionnaire in COPD patients were completed. Results: We found that in patients with UTCC/LTCC ratio > 0.8, UTCC had significant correlation with FEV1 and FEV1/FVC (R: 0.069, 0.055); Moreover significant correlation was found in UTCC, LTCC and UTCC/LTCC ratio with ACT score in this subgroup (R: -0.123, -0.092, -0.124)On the other hand in patients with UTCC/LTCC ratio > 0.9 , UTCC and LTCC had significant correlation with FEV1 (R: 0.07, 0.051). Conclusion: UTCC/LTCC ratio > 0.8, may be a predictor of obstructive pattern in patients. This is more important in some occations, for example during preoprative evaluation of a patient in an emergency conditions which there is no enough time for performing appropriate diagnostic tests such as spirometry to reveal the type and severity of obstructive pulmonary diseases.