Background: Eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP), characterized by eosinophil-predominant inflammation in mucosa, is a subject of much investigation. However, no satisfactory atraumatic clinical parameter has been established to date for prediagnosis of this condition. The aim of this study was therefore to compare the use of computed tomography (CT) scans with other clinical parameters in prediagnosis of eCRSwNP. Methods: This was a prospective cohort, single-institution study. Two hundred consecutive CRSwNP patients (123 eCRSwNP and 77 non-eosinophilic CRSwNP [neCRSwNP]) undergoing functional endoscopic sinus surgery in Beijing TongRen Hospital were recruited. Preoperative CT scan, skin-prick test (SPT), and oral fractional exhaled nitric oxide (FENO) measurements were performed in each patient and full blood count with differential analysis under the patients' regular condition was performed within 1 week before surgery. Logistic regression analysis and receiver operating characteristic (ROC) curve were used to assess the predictive value of clinical parameters. Results: History of surgery, onset of asthma, history of allergy, total Lund-Mackay scores, presence of osteoneo-genesis, FENO, and blood eosinophil counts were all significantly higher in the eCRSwNP group, compared to the neCRSwNP group. The ratio of the CT scores for the ethmoid sinus and maxillary sinus (E/M ratio) had the highest predictive value, with an area under the ROC curve (AUC) of 0.938. The cutoff point of > 2.59 for E/M ratio demonstrated a sensitivity of 94.2% and a specificity of 89.6% for eCRSwNP. Conclusion: The E/Mratio is a more useful predictor in diagnosis of eCRSwNP compared to the other clinical parameters. (C) 2016 ARS-AAOA, LLC.