Background: Osteitic bone is a feature of chronic rhinosinusitis (CRS), potentially playing a role in pathogenesis. Although seen after previous endoscopic sinus surgery (ESS), it is also a de novo feature in patients without prior interventions. In these patients, osteitis is associated with high tissue and serum eosinophilia. However, the impact of osteitis on prognosis is unclear. This study investigates the clinical and endoscopic outcomes between patients with and without osteitis after primary ESS. Methods: A prospective study of a cohort of previously unoperated patients with CRS undergoing ESS was performed. The sinuses were scored radiologically for osteitis using the Global Osteitis Score (GOS) and Kennedy Osteitis Score (KOS) preoperatively and were also scored dichotomously for the presence or absence of osteitis. Disease-specific quality of life (22-item Sino-Nasal Outcomes Test [SNOT-22]), nasal symptom score (NSS), endoscopic score (Lund-Kennedy), and clinical outcomes-including oral steroid use, frequency of nasal steroid irrigation, and infective exacerbations-were collected at baseline and 1 year postsurgery. The presence and extent of osteitis was assessed relative to clinical outcome. Results: Fifty-three patients were included (41.5% female, age 47.4 ± 13.8 years), 42.9% of which had radiologic osteitis. There was no significant association between the presence or severity of osteitis at the time of surgery and SNOT-22, NSS, or endoscopy scores at 12 months postsurgery. However, the presence of osteitis was associated with the need for a course of oral steroid postsurgery (odds ratio [OR]=4.17; p = 0.026). High tissue eosinophilia could not predict this alone (p = 0.55). There was no significant relationship between osteitis and the frequency of steroid irrigations or infective exacerbations. Conclusion: Osteitis in CRS is associated with the degree of eosinophilia and as a independent process it was associated with the need for a course of systemic corticosteroid over a 12-month period, but did it not affect overall disease control.