Object: To evaluate the usefulness of the lung volume measurement to diagnose the obstructive disease in patients with restrictive ventilatory impairment, postbronchodilator FEV1/FVC was compared with the flow of lung function interpretation. Methods: A retrospective study was conducted in 2,570 subjects with lung function tests including spirometry, lung volume measurement and postbronchodilator spirometry on the same date between April 2008 and December 2010 at Samsung Medical Center, Seoul, Korea. Postbronchodilator criteria was defined as postbronchodilator FEV1/FVC ＜0.7, and TLC criteria as TLC ≥80% predicted. Results: Seventy patients with normal FEV1/FVC and low FVC showed restrictive ventilator impairment. The flow of lung function interpretation indicated that 36 patients belonged to obstructive pattern more through TLC criteria. Of the 36 patients with an obstructive pattern, 18 (50%) patients were obstructive disease by postbronchodilator criteria. Of the 34 patients with a restrictive pattern, 15 (44%) patients were obstructive disease by postbronchodilator criteria. The agreement between the postbronchodilator criteria and TLC criteria was low, with concordance in 37/70 (53%) (κ=0.059, 95% CI: 0.494-3.245, p=0.622). Conclusion: Lung volume measurement might not be useful to diagnose the obstructive disease in patients with restrictive ventilatory impairment. If patients with restrictive pattern have risk factors and clinical symptoms, they might get a benefit from postbronchodilator spirometry to confirm the obstructive disease.