Conclusions The recurrence rate of IP in the current study is comparable to international and national studies. When the primary tumour was located in the frontal or the sphenoid sinus, the tumour seemed more likely to recur. Some recurrences were more than 2 years after primary surgery, suggesting continued need for long-term follow-up. The rate of malignant transformation in inverted papilloma cases has not changed in Denmark. Objectives Inverted papillomas are benign tumours located in the nasal cavity and paranasal sinuses. They are known for their tendency to recur after surgery and show invasive growth, causing bone remodulation and the association with malignant transformation. The introduction of endoscopic sinus surgery and computer aided sinus surgery over the last decades has made this tumour more approachable with less cosmetic and functional damage. The objective of this study is to establish whether the recurrence rate and the rate of malignant transformation of IP have changed with the application of these new techniques. Method A retrospective study between 1998-2008 including 88 cases with inverted papilloma. Results In total, 25.3% had recurrence. Combined surgical approach with endoscope/open approach had the lowest rate of recurrence. A malignant transformation in the postoperative histological examination was found in 8.9%.