A case of neuro-Behcet disease presenting as a thalamo-lenticular expanding lesion is reported. A 41-year-old female was admitted with mental deterioration and right hemiparesis. She had been suffering from recurrent oral and genital ulcers and erythema nodosum for several years before admission. Neurological examination on admission revealed poor mental activity, dysarthria and right hemiparesis. Lumbar puncture showed CSF pleocytosis. CT and MRI revealed a thalamo-lenticular expanding lesion. CT showed a homogeneous hypodense lesion of the left lenticulothalamic region, which was enhanced in the central part, exerting a mild mass effect. MRI also revealed the lesion better. The T2 weighted images showed a high intensity signal in the left thalamo-lenticular region and the left peduncle. The T1 weighted images showed a low signal in the corresponding areas with a central enhancement with Gd-DTPA. EEG, SPECT and angiography indicated normal findings. Histologic study of the brain biopsy tissue ruled out a tumor but did not show any specific diagnosis. The patient improved with steroid therapy. In conclusion, the clinical and radiological presentation of neuro-Behcet disease can mimic a cerebral tumor. In such cases, stereotactic biopsy is useful to exclude suspicion of a cerebral tumor.