The aim of this study was to compare volumetric parameters in the abnormal and normal posterior fossa using the Virtual Organ Computer-aided AnaLysis VOCAL technique to determine whether fetuses with an abnormal posterior fossa have different volumes. A prospective study was conducted on 17 fetuses with an abnormal posterior fossa including, Dandy Walker malformation (n = 6), vermian hypoplasia (n = 3), mega cisterna magna (n = 8) and 99 healthy control fetuses from 20 to 34 weeks' gestation. Measurement of the fetal cisterna magna and cerebellar volume was performed in the standard transcerebellar plane through the VOCAL method. To establish the correlation of volumes with gestational age, polynomial regression analysis was performed. For comparison between groups, univariate ANCOVA was performed using gestational age as a covariate. The reliability was analyzed by the intraclass correlation coefficient (ICC). Cerebellar volume and cisterna magna volume was correlated with gestational age. Posterior fossa volume was significantly larger in Dandy Walker malformation (DWM) (p < 0.0001) and mega cisterna magna (p < 0.0001) in comparison to the control group. In vermian hypoplasia group, cisterna magna volume does not seem to expand (p = 0.298). Cerebellar volume does not seem to change in subgroups when the influence of gestational age is discarded (p = 0.09). The ratio of cerebellar volume to the cisterna magna volume decreases significantly in abnormal fetuses (p < 0.0001). Good intraobserver and interobserver reliability was found for both cerebellum and cisterna magna measurements. Volume analysis may have a role in discrimination of different posterior fossa pathologies.