To evaluate the role of chest radiographs and CT scans in the diagnosis and treatment planning of lober atelectasis, 50 patients with lobar atelectasis were studied retrospectively. All cases were confirmed either by surgery(N=8) or bronchscopy(N=42). CT was superior to plain radiograph in cases of atypical form of lobar atelectasis (N=10). CT provided additional information in differentiating a benign from a malignant cause of atelectasis(N=47). For treatment planning, CT provided valuable information about the lesions in the mediastinum and chest wall(N=41), and to help demarcate the central mass from peripheral atelectasis(N=29). Inconclusion, CT is the mandatory imaging modality to diagnose and plan the treatment of lobar atelectasis.