Purpose : To determine the CT findings which distinguish consolidation-type bronchioloalveolar carcinoma fromnecrotizing pneumonia Materials and Method : This study involved ten patients with pathologically-provenconsolidation-type bronchioloalveolar carcinoma and 34 with necrotizing pneumonia proven pathologically either inthe laboratory or clinically. We retrospectively analyzed CT features including the enhancement pattern ofconsolidated lung, the presence and internal density of cavity within consolidated lung, CT angiogram sign,air-bronchogram, pleural enhancement, pleural effusion, and change in extrapleural tissue and its density. Result: CT findings in patients with necrotizing pneumonia showed higher attenuation in marginal (94.1%) and inner(85.3%) portions in consolidated lung than in muscles (p<0.005); the presence of cavity (91.2%, p<0.05) ; cavitywith fluid or air-fluid level (77.4%, p<0.005); pleural enhancement (88.2%, p<0.00003) ; pleural effusion (33.3%,p<0.05); and change in extrapleural tissue (64.7%, p<0.05). CT findings in patients with consolidation-typebronchioloalveolar carcinoma showed lower attenuation in marginal (90.0%) and inner (60.0%) portions ofconsolidated lung than muscles (p<0.005) and of cavity containing air (100%; p<0.005). However, air-bronchogramand CT angiogram signs were not helpful in differentiating the two groups. Conclusion : CT can help differentiateconsolidation-type bronchioloalveolar carcinoma and necrotizing pneumonia.