OBJECTIVES To investigate the importance of cerebral damage and retinopathy of prematurity (ROP) for visual impairment in preschool children born extremely premature and to determine the primary risk factor of the two. METHODS A clinical follow-up study of a Danish national cohort of children born extremely premature (gestational age, <28 weeks). The study sample consisted of 262 extremely preterm children born between February 13, 2004, and March 23, 2006, of whom 178 children (67.9%) participated. A matched control group consisted of 56 term-born children (gestational age, 37 to <42 weeks). All participants were identified through the National Birth Register and invited to participate in a clinical examination. The children were evaluated with regard to visual acuity, foveal sequelae, and maximum ROP stage and the presence of global developmental deficits (an indicator for cerebral damage) that was measured by the Ages and Stages Questionnaire. RESULTS Global developmental deficits and foveal sequelae occurred more often in extremely preterm children than in term-born control children and increased with ROP severity (χ2 test; P = .11 and P < .001, respectively). Global developmental deficits, moderate to severe foveal abnormality, and ROP treatment were independently associated with visual impairment (P < .05, for better and worse eyes). A stepwise multiple logistic regression for better-eye logarithmic visual acuities of 0.3 or greater (Snellen scale, ≤0.5) yielded an odds ratio of 8.7 (95% CI, 3.0-25.2; P < .001) for global developmental deficit and 6.3 (95% CI, 2.2-18.5; P < .001) for moderate to severe foveal sequelae. CONCLUSION Cerebral damage and ROP are independent risk factors for visual impairment in children born extremely premature, and cerebral damage may be the primary risk factor.