To evaluate the impact of smoking history and postdiagnosis smoking cessation on performance status (PS) and survival in patients with lung cancer. Patients with non-small cell lung cancer (NSCLC) who were referred to our pulmonary laboratory for evaluation for surgical resectability between January and November 2001 were reviewed. We investigated the association between smoking status after diagnosis and survival, as well as the change in PS from the initial status to status at 6 and 12 months after the diagnosis was established. The records were reviewed for 206 patients, of whom 93 (45%) were current smokers, 15 (7%) were never-smokers, and 98 (48%) were former smokers. Among the 93 smokers, 46 quit and 47 continued smoking after the diagnosis. Disease stage, patient demographics, treatment modalities, and comorbidities were similar between these two groups. While there was no significant association between smoking status after diagnosis and patient survival, those who quit smoking maintained a better PS at 0 to 6 months (odds ratio [OR], 7.09; 95% confidence interval [CI], 1.99 to 25.3; p = 0.002) and at 0 to 12 months (OR, 6.99; 95% CI, 1.76 to 27.7; p = 0.006) than those who continued smoking after the adjustment for disease stage, patient demographics, treatment modalities, and comorbidities. Patients who quit smoking after the diagnosis of NSCLC maintained a better PS at 6 and 12 months regardless of disease stage, age, race, sex, therapy types, and comorbidities than those who continued to smoke.