The purpose of this study is to compare traumatic brain injuries (TBI) and spinal cord injuries (SCI) patients' function and disability by using the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0); and to clarify the factors that contribute to disability. We analyzed data available between September 2012 and August 2013 from Taiwan's national disability registry which is based on the International Classification of Functioning, Disability, and Health (ICF) framework. Of the 2664 cases selected for the study, 1316 pertained to TBI and 1348 to SCI. A larger percentage of patients with TBI compared with those with SCI exhibited poor cognition, self-care, relationships, life activities, and participation in society (all p < 0.001). Age, sex, injury type, socioeconomic status, place of residence, and severity of impairment were determined as factors that independently contribute to disability (all p < 0.05). The WHODAS 2.0 is a generic assessment instrument which is appropriate for assessing the complex and multifaceted disability associated with TBI and SCI. Further studies are needed to validate the WHODAS 2.0 for TBI and SCI from a multidisciplinary perspective.