The aim of this study was to evaluate the incidence of visual function abnormalities in children with infantile hemiplegia, and the relation between visual abnormalities and type of lesion, as shown by brain MRI. Visual function was tested (grating acuity, visual field size, binocular optokinetic nystagmus [OKN], and ocular movements) in a group of 47 children with congenital or early acquired hemiplegic cerebral palsy (mean age 25 months, range 8 to 52 months). The cohort was subdivided into four groups according to MRI findings: brain malformations (n=5), abnormalities of the periventricular white matter (n=20), cortical–subcortical lesions (n=16), and non-progressive postnatal brain injuries (n=6). More than 80% of the children showed abnormal results in at least one visual test: acuity was the least impaired function, while visual field and OKN were abnormal in more than 50% of the cohort. No specific correlation could be identified between the type and timing of the lesions and visual function. Unlike adults with stroke, visual field defects were not always related to contralateral damage in the optic radiations or in the visual cortex. These results indicate that visual abnormalities are common in children with hemiplegia, and that they cannot always be predicted by MRI. All children with hemiplegia need a detailed assessment of visual function.