The purpose of this study was to determine if the severity of osteogenesis imperfecta (Ol) in childhood might have any influence on functional outcome. In a cross-sectional study, the functional outcome of 61 children with Ol was related to the three subtypes of the disease. Functional outcome was measured with the Dutch translation of the Pediatric Evaluation of Disability Inventory (PEDI). The PEDI measures capability and performance in three specific categories: “self-care, ” “mobility, ” and “social function.” We concluded that functional abilities, especially in the mobility category, were related to Ol subtype. The more severe the disease, the lower the score on mobility. In the self-care area, the score of all children ≤7.5 years of age, was within two standard deviations of the median. Despite severe disablement, children with Ol type III scored within the normal ranges. In older children with Ol, the relationship between Ol subtypes and functional ability became more pronounced. In children with the most severe disablement, there was a tendency, although not significant, for social function to be better developed. In children with a disease such as Ol, which affects posture, alignment, and growth, a severity-related functional ability profile seems to exist. Future multicenter research could further define a disease-related functional ability profile in Ol.