We reported 3 cases of hypersensitivity pneumonitis who had been exposed to polyurethane material containing diphenylmethane diisocyanate (MDI) for 1-12 weeks. They had cough, fever and dyspnea before admission. All 3 cases were diagnosed immunologically using anti-MDI antibodies. Chest HRCT findings of the 3 cases were different. Case 1 showed an organizing pneumonia (OP) pattern : patchy peripheral consolidation with air bronchogram and ground-glass opacities (GGO), and case 2 showed a nonspecific interstitial pneumonia (NSIP) pattern : consolidation and reticular shadows in both lower lobes. In addition, case 3 showed a hypersensitivity pneumonitis (HP) pattern : centrilobular GGO and diffuse granular shadows. All cases were successfully treated by corticosteroids alone. This suggests that different amounts of inhaled antigen can cause different HRCT findings.