OBJECTIVE: To test whether subscales should be used when analyzing the Sino-Nasal Outcome Test (SNOT). STUDY DESIGN AND SETTING: Prospective cohort study involved 87 acute NHS hospitals in England and Wales. RESULTS: With the use of exploratory factor analysis we found evidence for the existence of four unique constructs within the SNOT. Two constructs address symptoms (rhinologic and ear/facial) and two address aspects of health-related quality of life (psychological issues and sleep function). Subscales of the SNOT that correspond to these constructs provided clinically meaningful information over and above that provided by the SNOT total score on the type of surgical benefits gained by patients with different sino-nasal conditions. CONCLUSION: The SNOT is not unidimensional and a SNOT total score will mask variation in the true underlying constructs. SIGNIFICANCE: The SNOT would have greatly improved clinical use if it was scored with appropriate subscales. Such a measure would allow us to tease out the differential impact of sino-nasal conditions, in addition to allowing greater understanding of treatment effects.