Primary intracranial T cell type malignant lymphoma is extremely rare. Only 8 cases are reported in the literature so far. In this paper, a case with this type of malignant lymphoma is reported. A 41-year-old man was admitted because of abnormal behavior. Enhanced CT scan demonstrated high density mass and perifocal low-density area in the right frontal lobe, the right basal ganglia and the periventricular region. Specimen biopsied from right frontal lobe was submitted for histological examination. An immunohistochemical technique using monoclonal surface markers confirmed reactivity for LCA, MT-1, OKT-4 and OKT-8, while there was no reactivity for MB-1 and OKB-2. Pathological diagnosis was diffuse medium T cell type malignant lymphoma. Postoperatively, after 60 Gy irradiation, the tumor disappeared. There is no difference on CT findings between B cell type and T cell type malignant lymphoma.