Meningeal and intracerebral plasma cell granulomas are uncommon inflammatory lesions of unknown etiology. In this paper the diagnostic difficulties in two patients with meningeal plasma cell granuloma and one patient with intracerebral plasma cell granuloma are described. The first patient had an intracranial extra-axial lesion, which was first diagnosed as a meningioma. One and a half years later she underwent a second resection for recurrent tumor growth and the diagnosis of a meningeal plasma cell granuloma was made. The second patient was treated for a central nervous system B-cell lymphoma but proved to have an intracerebral plasma cell granuloma in retrospect 11 years later. In the third patient tuberculous meningitis was considered to be the most likely diagnosis because infratentorial contrast-enhanced thickened meninges (pachymeningitis) were found together with a high protein level in the cerebrospinal fluid and a positive Mantoux test. However, pathological examination of an extra-axial, cervical lesion that was operated upon revealed a meningeal plasma cell granuloma. These cases show the importance of diagnosing a meningeal or intracerebral plasma cell granuloma correctly, since it has both therapeutical and prognostic implications.