A case with brain metastasis involving bilateral middle cerebellar peduncles (bMCP) was reported. A 71-year-old male with gastric cancer was treated for multiple brain metastasis by gamma knife radiosurgery (GKR) in September, 2004. Two months after the initial GKR, MRI showed asymmetrical enhanced lesions involving bMCP. A few months later, MRI revealed an expansional infiltration of bMCP lesions. The patient had presented with headache loss of appetite, cerebellar ataxia, diplopia and slight dysmetria. PET showed 2-deoxy-2- [18F] fluoro-D-glucose (FDG) uptake of the bMCP lesions. The lesions were diagnosed as brain metastasis of gastric cancer. The patient underwent his second GKR (marginal dose : 19Gy, maximum dose 38Gy) MRI revealed the disappearance of the tumors 3 months after the second GKR. One year later, the patient showed no evidence of recurrence. For the last time, our case was diagnosed as brain metastasis from gastric cancer without meningeal carcinomatosis. It was suggested that FDG-PET can provide additional information about the lesion of bMCP. GKR may be useful to treat the tumor in bMCP.