Inversion duplication 8p is a rare chromosome disorder characterised by severe mental retardation, minor facial dysmorphisms, and corpus callosum agenesis. Few cerebral imaging studies have been reported. We describe 9 patients with an inversion duplication 8p, involving variable segments of the short arm of chromosome 8. MRI was performed in 8 patients and 2 patients underwent CT scanning. The images were systematically reviewed. All patients suffered from severe mental retardation. Head circumference was between 0 and + 2 SD in 7 patients. The corpus callosum was absent in 6, and thin (but complete) in 3 patients. Hypoplasia of the (inferior) cerebellar vermis was observed in 6 patients. Enlargement of the ventricular system and associated hippocampal maldevelopment were found in all patients. The supratentorial external CSF spaces were enlarged in 6 patients, and in 3 patients there was a remarkable enlargement of the retrocerebellar arachnoidal space. Cerebral white matter showed mildly delayed myelination in 7 patients, and periventricular lesions of variable extent in 6 patients. The pattern of imaging abnormalities was non-specific, but remarkably similar between patients. We found no correlation between the severity of the clinical features, imaging results, and extent of the chromosomal aberration.