Objectives: So far, there are only two studies evaluating the relation between the small volume of the posterior cranial fossa (VPCF) and the occurrence of HFS, both on Asian population. The aim of the study was to determine small VPCF and arterial hypertension (AH), as risk factors for hemifacial spasm (HFS) and their relation to neurovascular conflict (NVC) in Polish Caucasian-origin patients. Materials and methods: The study included 60 patients with idiopathic HFS and 60 healthy volunteers matched by sex and age. AH was defined according to WHO. The VPCF measured the volume of the prepontine, prespinal and both cerebellopontine angle cisterns in MRI scans. Results: There were no significant differences between occurrence of AH and the VPCF of patients and controls but the mean VPCF in women was significantly smaller than in men, In the multivariate regression analysis model only NVC was the statistically significant. In the subgroup of >50-year-old patients the most dominant risk factor was NVC (OR 71.09; 95% CI 21.08–239.77; p = 0.0000), followed by the AH duration (OR 1.07; 95% CI 1.00–1.16; p = 0.047). In the subgroup of <50 years, NVC was also the dominant risk factor, followed by the lower VPCF (Walad test: OR 0.4; 95% CI 0.16–1.04; p = 0.045). Conclusion: There was no significant difference in VPCF and in frequency of AH diagnosis in HFS patients and age- and sex-related controls, but the logistic regression analysis showed that small VPCF and AH duration are risk factors of HFS in younger and older patients respectivel