The diagnosis of leptomeningeal metastasis is often difficult and usually requires the demonstration of malignant cells in the cerebrospinal fluid. Neuroimaging, however, may establish or support the diagnosis in some patients. Radiographic abnormalities consistent with or suggestive of leptomeningeal metastasis include leptomeningeal, subependymal, dural, or cranial nerve enhancement; superficial cerebral lesions; and communicating hydrocephalus. We evaluated 137 cancer patients with clinical symptoms suspicious for leptomeningeal metastasis with neuroimaging or cerebrospinal fluid cytology or both. Neuroimaging findings were abnormal in 70 of 128 tested patients; cytology was performed in 58 of these 70 and the results were positive in 37. Conversely, cytological findings were positive in 53 of 115 tested patients; neuroimaging was performed in 49 of these 53 and the findings were abnormal in 37 (26/29 solid tumors and 11/20 hematological tumors). Of the total series of 137 patients, leptomeningeal metastasis was diagnosed in 77; in 24 (31%) the diagnosis was made on the basis of clinical picture and abnormal neuroimaging alone. Neuroimaging is a valuable tool in the investigation of leptomeningeal metastasis in the cancer population, and the presence of typical clinical features together with appropriate neuroimaging abnormalities is adequate to make the diagnosis of leptomeningeal metastasis even if cerebrospinal fluid cytological results are negative.