We report on the neuroradiological studies performed on three infants with capillary haemangioma (CH) of the head and neck with associated posterior fossa and arterial abnormalities. Posterior fossa malformations were represented by cerebellar hemispheric and vermian hypoplasia and cerebellar cortical dysgenesis, whereas arterial anomalies included bilateral agenesis, kinking, and looping of the internal carotid arteries. One patient had marked exophthalmos due to intraorbital CH. We suggest that these patients had an incomplete phenotypic expression of PHACES syndrome, a vascular phakomatosis characterised by the variable association of posterior fossa malformations, CH, arterial anomalies, coarctation of the aorta and cardiac defects, eye abnormalities, and sternal and medioventral defects. Evidence suggests that PHACES syndrome is not a random association but a true phakomatosis; further studies are awaited to shed light on a possible genetic background. The phenotypic spectrum is broad and still largely unexplored, and precise diagnostic criteria have not yet been identified. A causal teratogenic influence, possibly related to anomalous expression of vascular growth factors and their modulators, is suggested to occur between gestational weeks 3 and 5.5