Purpose: The aim of this study was to evaluate the effect of a breathing exercise intervention by measuring pulmonary function test (PFT) three times; preoperative, 3rd and 5th day after operation. Methods: This study was designed as a nonequivalent control group pretest-posttest design. A total of 55 patients with lung cancer were recruited from a C-university hospital in H-gun, Korea from January to December 2008. Results: ‘Forced Vital Capacity (FVC)’ and ‘Forced Expiratory Volume in 1 second (FEV1)’ were significantly improved in the experimental group than those in the control group (p<.05). Conclusion: Breathing exercise intervention was found to be effective in improving pulmonary function among lung cancer patients underwent lung lobectomy. Thus, the breathing exercise can be applied in hospitals and communities for patients with lung cancer as one of the nursing intervention modalities for their better postoperative rehabilitation.