OBJECTIVE. Reducing pulmonary volume through implantation of endobronchial valves is a major interest to improve exercise tolerance and survival in patients with severe emphysema. The primary aim of this study was to evaluate how well CT-determined fissure integrity predicts interlobar collateral ventilation. The secondary objective was to show whether there is a relationship between the size of fissural defects and the presence of collateral ventilation. MATERIALS AND METHODS. Thirty patients with heterogeneous emphysema (postbronchodilator forced expiratory volume in 1 second [FEV1] = 20–50% predicted and > 50% of emphysema in a lobe) underwent collateral ventilation measurements with a catheter through an occlusive balloon within this target lobe during flexible endoscopy. Two senior thoracic radiologists studied the fissures on thoracic high-resolution CT. RESULTS. Collateral ventilation …