Abstract: Objective: Purpose to improve the acquaintance about diffuse Bronchiolo-alveolar Carcinoma(DBAC),and make a correct diagnosis at the early stage, so that decrease the misdiagnosing. Method: Retrospectively analyzed the CT misdiagnosing about 15 cases of diffuse Bronchioloalveolar Carsinama(DBAC). Result: Among these misdiagnosing cases,6 were misdiagnosed as pneumonia,7 were mis-diagnosed as tuberculosis, 2 were misdiagnosed as silicosis. Conclusion: Though CT finding of early-stage of diffuse bronchioloalveolar carcinoma showed no particularity, but improve the acquaintance about diffuse Bronchioloalveolat Carcinoma(DBAC) and using some related method is helpful to correct diagnosis.