PURPOSE Families of patients with traumatic brain injury (TBI) often perceive patients' functional capabilities differently from patients themselves. Research documents inconsistent findings regarding direction of differences. Differences have implications for family support and are germane to clinicians' treatment planning during rehabilitation. We compared two analytic approaches to patient-family differences in ratings of 30 functional tasks: (a) comparing patients' and families' mean scores in domains derived from factor analysis versus (b) examining differences on a task-by-task basis. METHOD In-home interviews were conducted with 83 outpatients with TBI at a Veteran Affairs polytrauma clinic and for each a family member, using the Patient Competency Rating Scale with both. RESULTS Principal components analysis identified three functional domains--cognitive, interpersonal/emotional and physical--with significant patient-family differences in the cognitive domain only (family competency ratings were higher). By contrast, task-by-task examination showed significant veteran-family differences in 12 items, mostly in interpersonal/emotional functioning, with mixed directions of differences. The task-by-task approach thus revealed a different picture of patient-family differences than examination by functional domains. CONCLUSIONS Grouping tasks by domains may obscure important differences in functional ratings. Examination of patient-family differences by task has clinical applications for helping patients and families to manage TBI symptoms and for treatment planning. IMPLICATIONS FOR REHABILITATION Differences in functional capacity ratings by patients with TBI and their family members are not well understood, with past research demonstrating inconsistencies in direction of difference. Differences in ratings may affect family relationships and may inform clinicians' treatment plans. The study showed that different approaches to analyzing the same data yield two distinct pictures of patient-family differences. Examining patient-family differences by specific tasks is clinically meaningful. The Competency Rating Scale could be used as a clinical tool with patients and families. Its use may improve family understanding of the patient's strengths and struggles and also guide treatment planning.