Here we report a case of mainstem bronchus obstruction due to a carcinoma in situ. Preinvasive lesions, such as carcinoma in situ, are usually small and limited to the bronchial wall. This exceptional presentation shows a tumor growth large enough to completely occlude the right mainstem bronchus. The endoluminal lesion was removed using rigid bronchoscopy. The patient, not eligible for a local treatment, has been treated with surgery.