Normal pressure hydrocephalus (NPH) is characterised by gait disturbance, urinary incontinence and dementia. Even though dementia is a cardinal symptom of NPH, there is few data available concerning cognitive functioning. The aim of this observational case-control study was to evaluate the use of neuropsychological (NPSY) tests prior and after spinal tap test, which might be helpful for diagnosis, treatment and as a prognostic factor for shunt surgery. 15 patients with NPH and 18 controls were examined with eleven different tests covering all neuropsychological domains on two consecutive days. The second examination in NPH patients was 1 day after a spinal tap of 30-50 ml cerebrospinal fluid. A significant difference between NPH and controls in the change between baseline and 1 day after spinal tap was only observed in MMSE. In the domains of visuo-constructive function and attention, controls performed slightly better at day one compared to baseline, which could be interpreted as a learning effect, but after adjusting for multiple testing none of the P values were significant. In contrast to other reports, the MMSE seems to provide a sensitive evaluation of the response to spinal tap in NPH patients and might therefore be included into the routine work up of NPH patients. All other NPSY tests showed less prominent changes within 1 day after spinal tap.