Plasma cell granulomas, inflammatory pseudotumours and myofibroblastomas are synonymous with characteristic plasma cell infiltration in various body organs including the pancreas, liver, retroperitoneum and mediastinal structures causing idiopathic fibrosclerosis. Recently, a new concept has arisen regarding the relationship between immunoglobulin (Ig)G4-positive cell infiltration and idiopathic systemic fibrosclerosis. We report two cases showing IgG4-positive cell infiltration in the lung presenting as lung nodules with or without extrapulmonary manifestations.