Abstract We describe a single case of a polymalformational syndrome in which the MR findings were of great help in the final diagnosis of Smith-Lemli-Opitz syndrome (SLOS) type I. MRI was performed for evaluation of the brain morphology since the clinical and laboratory findings were suggestive but not unequivocally indicative of SLOS. MRI findings of frontal lobe hypoplasia, cortical migration defect, and abnormalities of median line structures prompted the final diagnosis of SLOS.