Chronic suppurative otitis media (CSOM) is characterized by intermittent or continuous otorrhea lasting for longer than 6 weeks. Most cases can be treated conservatively using antibiotic drops and oral antibiotics. However, some cases will not respond to conservative treatment and demonstrate persistant discharge. In these cases, especially if a CT-scan shows opacification of the mastoid air cells, a mastoidectomy can be considered as treatment modality. In recent years, obliteration of the mastoid cavity following mastoidectomy is gaining popularity. However, the effectiveness of obliterating the mastoid in comparison to mastoidectomy alone is uncertain for CSOM. In this retrospective cohort study, our aim is to compare mastoidectomy to mastoidectomy + mastoid obliteration in a cohort of patients suffering from CSOM with mastoid involvement. The hypothesis is that obliterating the mastoid cavity will result in a higher frequency of dry ears and in a lower frequency of revision surgeries.