An apparatus for endobronchial ablation of a tumor is provided. The apparatus has an ablation catheter and a guide facility to be inserted into the bronchial system, a sheath defining a guide channel for the ablation catheter, a closing apparatus for a bronchial arm, and an aperture allowing airtight insertion of the ablation catheter into a bronchial arm blocked by the closing apparatus. The ablation catheter and/or the guide facility have a suction apparatus for sucking air out of a bronchial arm blocked off by the closing apparatus.
