We studied 11 patients undergoing a routine lumbar puncture to determine if there were cerebrospinal fluid leaks at the puncture site and whether the maximum volume of leakage correlates with a lumbar puncture headache. Patients completed a headache questionnaire before and after the lumbar puncture. Limited magnetic resonance imaging of the lumbar spine was obtained 8 to 36 hours after the lumbar puncture and two patients also had later imaging. In a blinded fashion, the largest diameter of cerebrospinal fluid leakage into the paraspinous area was determined from T2 weighted magnetic resonance images and the maximum possible fluid volume was calculated. Six patients had a small cerebrospinal fluid leakage (< 10 mL), two had a medium leakage (10 to 110 mL), and three had a large leakage (> 110 mL). The volume of cerebrospinal fluid leakage did not correlate with occurrence of a lumbar puncture headache. The study demonstrates that cerebrospinal fluid usually leaks into the paraspinous area after a lumbar puncture, but the volume of escaped fluid does not correlate with a lumbar puncture headache.