Although ultrathin bronchoscopes are suggested to have comparable abilities to conventional bronchoscopes in diagnosing peripheral lung lesions, how to introduce ultrathin bronchoscopes into bronchoscopic examination is still to be determined. In our first study, 35 patients with peripheral lung lesions underwent ultrathin followed by conventional bronchoscopy to compare their diagnostic abilities. The diagnostic rate was 54.3% in conventional bronchoscopy alone, 60.0% in ultrathin bronchoscopy alone, and 62.8% in the combination of the two. In the next study, we introduced a rapid cytology test of the material obtained in conventional bronchoscopy. When malignant cells were not detected in the material by the rapid cytology, ultrathin bronchoscopy was immediately conducted. Thirty-two patients with negative rapid cytology were enrolled in this study. Ultrathin bronchoscopy resulted in diagnostic materials in 59.3% of these cases. Ultrathin bronchoscopes showed better access to the lesions than a brush or a curette introduced through conventional bronchoscopes. We conclude that ultrathin bronchoscopes have a comparable ability to conventional ones in diagnosing peripheral lung cancer even when used alone, and become a good complement to conventional ones by introducing the rapid cytology test.