To review the clinical characteristics, prevalence and outcomes of chronic rhinosinusitis patients with a hypoplastic maxillary sinus who underwent functional endoscopic sinus surgery.

A retrospective review was performed for the 814 consecutive, elective functional endoscopic sinus surgery procedures performed at an academic centre from 2010 to 2020, to identify patients with a hypoplastic maxillary sinus.

A total of 56 hypoplastic maxillary sinus cases were detected. Maxillary sinus hypoplasia presented unilaterally in 20 cases and bilaterally in 18 cases. Of the maxillary sinus hypoplasia cases, 38 were type I, 17 were type II and 1 was type III. The average Lund–McKay score was 8.6. No major post-operative complications were reported. Four patients had minor complications and one had persistent post-nasal drip.

Functional endoscopic sinus surgery is a safe and effective procedure for improving the clinical condition of patients with a hypoplastic maxillary sinus; however, careful pre-operative radiological evaluation, identification of intra-operative endoscopic landmarks and use of additional techniques may be essential to achieve satisfactory results and avoid possible serious complications.