Background: ‘Immunoglobulin G4 (IgG4)-related disease (IgG4-RD)‘ comprises multi-organ diseases including pulmonary disorders. Typical patients show extrathoracic lesions. We compared cases with or without extrathoracic lesions. Method: Tokyo Diffuse Lung Diseases Study Group retrospectively examined data from 44 patients suspected of IgG4-RD. Diagnostic criteria included high serum IgG4 level (>135mg/dL). Lung biopsy specimens showed massive IgG4+ plasma cell infiltrations (IgG4+/IgG+ >40% and >10/high power fields). Computed tomography and pathological findings were evaluated by diagnostic radiologists and pathologists independently. Final diagnoses were made by open panel conference. Result: Of 44 patients, 20 had extrathoracic lesions and 24 had intrathoracic lesions alone. We classified 20 extrathoracic lesion cases as IgG4-related RD (A group) and 15/24 cases without extrathoracic lesions as suspected disease entity such as non-specific interstitial pneumonia (B group). In A, radiological findings included hilomediastinal lymphadenopathy, bronchial wall and bronchovascular (BV) bundles thickening, interlobular septal thickening and/or periBV consolidation. Pathological findings showed abundant lymphoplasmacytic inflammation in interlobular septa, periBV interstitium, bronchus and pleura. Phlebitis, angiitis, granulation tissue, and/or fibrosis were also observed. The remaining 9 (C group) showed similar pulmonary involvement as A excluding extrathoracic lesions. Conclusions: There is C group with similar radiological and pathological features as A excluding extrathoracic lesions, and it might be "lung-limited IgG4-RD". Further discussion is necessary for diagnostic consensus of lung-limited disease.