Keratocystic odontogenic tumour (KOT or KCOT) is defined by the WHO to be 'a benign uni- or multicystic, intraosseous tumour of odontogenic origin'. In 2005, the World Health Organization renamed the lesion; previously known as an odontogenic keratocyst (OKC) as the KCOT. WHO recommends the term KCOT as it reflects its neoplastic nature. In this case report, a 21-year-old female with a histologically proven large parakeratinised KCOT of the right mandible underwent treatment that involved a 14-month period of decompression, followed by enucleation (with Carnoys application) of the residual cyst. During the period of decompression, a custom made removable mandibular chrome-cobalt appliance was used to hold the decompression tube in the oral cavity.