Intravoxel incoherent motion MRI was used to assess six intracranial, extraaxial cysts and tumors including two epidermoids, two cystic acoustic schwannomas, and two arachnoid cysts. A maximum gradient strength of 0.7 g/cm was used simultaneously along all axes (maximum gradient beta value: 445 s/mm2) and comparisons were made with an external water phantom. In epidermoid tumors the apparent diffusion coefficient (ADC) was similar to that of normal brain, thus indicating their solid nature. In acoustic schwannomas an ADC similar to the external water phantom indicated cystic components, whereas an ADC similar to brain was found in the solid portions of the tumor. The ADC of arachnoid cysts was similar to that of the water phantom, indicating their fluid nature. Due to macroscopic CSF flow, cisternal CSF showed high ADC, which enabled epidermoid tumors to be highlighted.