Pulmonary arteries of the right middle (RML) and right lower (RLL) lobes lie toward the lung periphery relative to their corresponding bronchi, i.e., along their lateral or posterior aspects. In contrast, those of the right upper lobe (RUL) tend to be located along the medial or anterior aspect of the bronchi. We postulate that a reversal of the normal bronchoarterial relationship at the lung base may indicate combined RML and RLL collapse. We evaluated bronchoarterial relation by computed tomography (CT) and posteroanterior (PA) chest radiographs n patients with combined RML and RLL collapse. On PA chest radiographs, an inverse bronchoarterial relationship could be recognized in the lower perihilar region in seven of 10 patients. In the 10 patients with complete collapse of both the RML and RLL, CT disclosed that the normal bronchoarterial relationship of the RUL was preserved, despite caudal extension of the RUL. In no case were arteries visible along the lateral aspect of bronchi. Thus, on frontal radiographs, when the bronchoarterial relationship in the right lower lung is inverse to that of normal subjects, combined collapse is strongly suggested.