Fine capillary network develops in the tracheo-bronchial tree and airway diseases cause several bronchial mucosal changes. A newly developed side-viewing high magnification bronchovideoscope (XBF-200HM3, Olympus Medical Systems Corp) was used in this study. This bronchovideoscope enabled us to observe bronchial mucosa with a high magnification of approximately 100 times. Five patients with lung tumor were enrolled into this study. The patients underwent conventional bronchoscopy and subsequent high magnification bronchovideoscopy. After lobectomy operation, the high magnification images were compared with microscopic findings of bronchus. Our results indicated that subepithelial microvessels were clear appearances with thin mucosa whereas vague appearances in thick mucosa. In conclusion, we suspect that the thickness of mucosa influence on the appearances of the microvessels in large airways.