Early diagnosis of cerebral abscess, which is decisive for the prognosis, is often complicated by the lack of clinical signs. Conventional computed tomography and magnetic resonance imaging cannot always differentiate a cystic or necrotic tumor from an abscess. An abscess is therefore sometimes misdiagnosed as e.g. a glioblastoma or metastasis. Unfortunately, this is sometimes seen at our department and could maybe have been prevented. Diffusion-weighted imaging and apparent diffusion coefficient facilitate differentiation between cerebral tumor and abscess with a sensitivity of 95.2% (76.2-99.9%) and a specificity of 95.7% (78.1-99.9%).