PURPOSE: Paranasal sinus osteomas are slow-growing, benign bony tumours that when larger than 30 mm, they are termed 'gigantic'. Special considerations apply for tumours of this calibre, and their rarity renders their management fairly controversial. This study seeks to contribute to an increased understanding concerning their management by presenting a 12-year experience from a single institution. METHODS: Retrospective review of files of patients treated for a gigantic paranasal sinus osteoma from January 2008 to December 2019. Additionally, all patients were prospectively reexamined in early 2020 for late complications or clinical recurrence. RESULTS: Ten patients were included, with a mean age of 53.8 years (range: 23-77 years). The leading presenting findings were proptosis (80%) and diplopia (70%). Transient visual impairment was remarkably frequent (30%). Five patients were managed with an open approach, two with an endoscopic, and three with a combined technique. The most common adverse characteristics that dictated the use of an open approach, alone or in combination with an endoscopic approach, were the involvement of the anterior wall of the frontal sinus (40%), erosion of its posterior wall (30%), and a far-anterior intraorbital extension (30%). No major postoperative complications were observed, and also no recurrences. CONCLUSION: Our study illustrates that these tumours may require a different management attitude. Despite substantial advances in the endoscopic management of benign sinonasal tumours, managing these massive tumours solely endoscopically could, in many cases, be inefficacious or impossible. Open approaches remain valuable, representing a safe and straightforward method for adequate exposure.