Background: Eosinophilic chronic rhinosinusitis (eCRS) is an inflammatory endotype of CRS. Contemporary treatment includes creation of a “neo-sinus” cavity and postoperative corticosteroid irrigations. Not all patients gain control with local therapy. This study aims to determine, in patients with polyp recurrence, the most common sinuses involved. Methods: A prospective case-series was conducted on consecutive adult (≥18 years) post-FESS eCRS patients followed for a minimum of 12 months. All patients had a neo-sinus cavity created surgically and used corticosteroid irrigations daily for 3-6 months, then tapered to disease control. Sinus cavities were assessed by endoscopy on last follow-up. Polyp recurrence was defined as a score of 5 or 6 in the MLMES in ≥3 sinus cavities. Patient-reported outcomes based on SNOT22 and NSS, frequency of corticosteroid irrigations, and courses of systemic antibiotics and corticosteroid were collected. The pattern of sinus involvement was analyzed. Result: A total of 342 sinus cavities were assessed (mean ± standard deviation, 54.9 ± 13.4 years, 43.2% female). Polyp recurrence occurred in 4.3% (6.4% of patients, n = 7 unilateral) of sinus cavities. Frontal and ethmoid sinus cavities were most affected in those with polyp recurrence, compared to the maxilla and sphenoid (100% vs 100% vs 53% vs 53%, p < 0.01). Although those patients with polyp recurrence utilized more systemic corticosteroids courses per year (0.4 ± 0.4 vs 0.1 ± 0.3, p < 0.01), the use of corticosteroid irrigations was similar (% >4/week; 66.7% vs 48.9%, p = 0.13). Prior surgery was more common in patients with polyp recurrence (86.7% vs 53.5%, p = 0.01). Conclusion: The frontal and ethmoid sinuses were most affected in those patients with polyp recurrence. Whether the disease is more active in this location or topical therapy has limited access requires further evaluation.