The charts and X-rays of one hundred and fifty-nine consecutive children with Osteogenesis imperfecta (OI) were reviewed to evaluate the functional outcome of OI patients with upper limb deformities. The patients were classified according to Sillence classification modified by Glorieux (Type I: 51, Type III: 33, Type IV: 54 and Type V: 21). The functional outcome was measured using Pediatric Evaluation of Disability Inventory (PEDI) based on self care and mobility scores, and results were compared between the patients with upper limb deformities and the ones without upper limb deformities. There was significant negative correlation between the functional outcome and the total deformity angle. Osteogenesis imperfecta is a genetic disorder of bone fragility. There are also some angular deformities of upper and lower limbs secondary to fracture and abnormal structure of bones in many OI patients depending on the severity of their condition. Corrective surgeries to the lower extremities are established interventions and used extensively but surgical correction of upper limb deformities is less frequent. The purpose of this study was to measure the severity of upper limb deformities in children with OI and the child’s functional level in order to answer the question: “Do upper limb deformities significantly affect function and therefore require surgical intervention?” Upper limb deformities were measured and classified using AP and lateral Xrays of the arms and forearms. The site and direction of deformities were recorded. Total deformity angle was calculated as the sum of right and left arm and forearm deformity angles. Upper limb deformities were classified into four groups according to the severity of deformity angles. The mean self care scores of PEDI were significantly low only in the group with severe and bilateral deformities but mobility scores were dramatically decreased in both the moderate and severe deformity groups. Deformities of the upper limbs in OI limit not only mobility but also self care functions. Therefore they require more attention and it may be necessary to broaden the indications for surgery.