Tumefactive demyelinating lesions (TDLs) are misdiagnosed frequently. To investigate the characteristics of TDLs, clinical and radiological data from nine cases with TDLs were analyzed after admission. All cases underwent surgery and pathological examination; some received postoperative steroid therapy. Onsets were mostly within 3 weeks and main presentation included intracranial hypertension, extremity weakness, epilepsy, and visual disturbance. Symptoms in children were acute and severe, frequently including headache, vomiting, and visual disturbance. Most intracephalic lesions were in cerebral hemispheres. All intraspinal lesions were in cervical segments. Radiological features included mass effect, perifocal edema and enhancement (of which open-ring enhancement was diagnostic), and decreased relative cerebral blood volume. Intraoperative frozen section did not confirm the diagnosis, while postoperative paraffin section did confirm it (by evidence of macrophage infiltration). The patients responded well to steroid therapy and no relapse was found during following up. Thus, intensive analysis of both clinical and radiological data may provide some clues for diagnosis. For suspected cases, it is advisable to take steroid therapy or undergo advanced radiological examinations, such as serial magnetic resonance spectroscopy. However, in difficult cases, pathological evidence is beneficial to a final diagnosis.