We evaluated the neuropsychological status of 13 adults patients with Marfan syndrome. All subjects were administered the same neuropsychological test battery that included nine measures covering a broad range of cognitive abilities such as attention and concentration, learning and memory, and verbal and non-verbal abilities. Compared to a control group of 13 healthy subjects matched for sex, age and verbal intelligence, Marfan patients only performed significantly worse on tests measuring sustained visual attention and visuoconstruction. Although these tests use visual material and depend on visual perception and processing, the visual acuity problems associated with the syndrome could not explain these differences, nor could the use of beta-blocking medication or the presence of joint hypermobility. The findings suggest that problems with sustained visual attention and visuoconstruction may be present in Marfan syndrome over and above visual acuity problems and other phenomena associated with the disease. Further research on the neuropsychological aspects of Marfan syndrome is needed, using larger patient groups and more adequate control groups such as non-affected siblings and matched controls with similar visual impairment.