Concurrent temozolomide (TMZ) and radiotherapy became the new standard of care for patients diagnosed with glioblastoma multiforme (GBM). Recently, there has been an increasing awareness of progressive and enhancing lesions on MR images immediately after treatment. These lesions may be a treatment effect, so-called pseudoprogression. We experienced one case pathologically and clinically diagnosed as pseudoprogression. The lesion showed a high apparent diffusion coefficient on diffusion-weighted imaging, low blood volume on perfusion imaging, and low uptake of 18F-fluorodeoxyglucose on positron emission tomography. The lesion was pathologically diagnosed as pseudoprogression after additional surgical resection.