BACKGROUND: Although the overall prognosis of patients with lung cancer is poor, highly effective treatment exists for the small subset of patients with early lung cancer(carcinoma in situ/micro- invasive cancer). But very few patients have benefit from them because these lesions are difficult to detect and localize with conventional white-light bronchoscopy. To overcome this problem, a Lung Imaging Fluorescence Endoscopic device(LIFE) was developed to detect and clearly delineate the exact location and extent of premalignant and early lung cancer lesions using differences in tissue autofluorescence. PURPOSE: The purpose of this study was to determine the difference of sensitivity and specificity in detecting dysplasia and carcinoma between fluorescence imaging and conventional white light bronchoscopy. MATERIAL AND METHODS: 35 patients (16 with abnormal chest X-ray, 2 with positive sputum study, 2 with undiagnosed pleural effusion, 15 with respiratory symptom) hale been examined by LIFE imaging system. After a white light bronchoscopy, the patients were submitted to fluorescence bronchoscopy and the findings of both examinations have been classified in 3 categories(class I, II, III). From of all class II and III sites, 79 biopsy specimens have been collected for histologic examination: a comparison between histologic results and white light or fluorescence bronchoscopy has been performed for assessing sensitivity and specificity of the two methods. RESULTS: 1) Total 79 sites in 35 patients were examined. Histology demonstrated 8 normal mucosa, 21 hyperplasia, 23 dysplasia, and 27 microinvasive and invasive carcinoma. 2) The sensitivity of white light or fluorescence bronchoscopy in detecting dysplasia was 60.9% and 82.6%, respectively. 3) The results of. this study showed 70.3 % sensitivity for microinvasive or invasive carcinoma with LIFE system, versus 100% sensitivity for white light in 27 cases of carcinoma. The false negative study of LIFE system was 8 cases(3 adenocarcinoma and 5 small cell carcinoma), which were infiltrated in submucosal area and had normal epithelium. CONCLUSION: To improve the ability to diagnose and stage more accurately, fluorescence imaging may become an important adjunct to conventional bronchoscopic examination because of its high detection rate of premalignant and malignant epithelial lesion. But, it has limitation to detect in submucosal infiltrating carcinoma.