RI cisternography (RIC) and CT myelography (CTM) are used to detect cerebrospinal fluid (CSF) leakage in patients with intracranial hypotension. Although several reports claimed that RIC had a risk of false positives and false negatives, no study has been made to directly compare CTM and RIC. In our research we selected 18 cases (8 men and 10 women) of spontaneous intracranial hypotension who met the diagnostic criteria of the international classification of headache disorders, 2nd edition, and compared the findings of RIC and CTM. Results: In RIC, indirect signs (delayed ascent of the RI or early bladder RI accumulation) were observed in all cases, but a direct sign (paravertebral RI accumulation) were observed in 12 cases (67%). In CTM, all cases (100%) showed an epidural collection of contrast media. An epidural collection of intrathecally administered contrast media is proof that active CSF fistula is present in patients with spontaneous intracranial hypotension. CTM is more accurate and sensitive than RIC in detecting CSF leakage in patients with spontaneous intracranial hypotension.