This study aimed to validate the use of the Adelaide Disease Severity Score for the assessment of chronic rhinosinusitis. A prospective cohort study supplying level 2b evidence. Forty-eight patients, scheduled for endoscopic sinus surgery for failed management of chronic rhinosinusitis, completed the Sino-Nasal Outcome Test 22 and the Adelaide Disease Severity Score tool (the latter assessing symptoms (i.e. nasal obstruction, rhinorrhoea, post-nasal drip, headache or facial pain, and olfaction) and quality of life). Lund-Mackay computed tomography scores and Lund-Kennedy endoscopic scores were also recorded. The Adelaide Disease Severity Score results were then compared with those of the other three tools to assess correlation. Mean scores (95 per cent confidence intervals) were 22.31 (21.47-24.15) for the Adelaide Disease Severity Score and 30.6 (27.15-34.05) for the Sino-Nasal Outcome Test 22; there was a statistically significant correlation (Spearman coefficient = 0.45; p = 0.0015). A statistically significant correlation was also noted with the Lund-Mackay score (p = 0.04) and with the Lund-Kennedy score (p = 0.03). The Adelaide Disease Severity Score is a simple, valid tool for clinical assessment of chronic rhinosinusitis, which correlates well with the Sino-Nasal Outcome Test 22, Lund-Mackay and Lund-Kennedy tools.