Objective: Intracranial hypotension (ICH) can be a challenging diagnosis, as cerebrospinal fluid leaks may be difficult to confirm, patients may have other causes for clinical symptoms and imaging findings can be nonspecific, particularly in the setting of comorbidities. We investigate the use of brain diffusion measurements [apparent diffusion coefficient (ADC) values] in the assessment of ICH. Methods: 13 cases of ICH were identified retrospectively based on imaging findings and their clinical histories were compared with 13 control subjects. Regional ADC values and average diffusion constant (D av ) from brain slice ADC histograms were measured. Results: ADC values trended higher in all brain regions in patients with ICH than those in control subjects, with statistically significant differences in frontal white matter, mid-brain and deep grey structures. D av determined by a single-slice ADC histogram was significantly higher in patients with ICH than in the control group (p 5 0.008). In two cases followed longitudinally, D av correlated with the patient's symptoms and decreased towards normal value with blood patch. In one case, decreased D av correlated with the formation of subdural collections. Conclusion: Cerebral oedema as assessed by increased ADC is strongly correlated with ICH (10 of 13 cases). Histographic analysis of ADC values may offer increased accuracy of ADC measurement. ADC value assessment in the determination of ICH may be particularly useful in complex clinical cases, where treatment is followed over time or where gadolinium is not used and meningeal enhancement cannot be assessed. Advances in knowledge: This article investigates the use of brain diffusion measurements in the assessment of ICH in the clinical setting.