This thesis titled ‘Patients with chromosomal disorders and their dental treatment: Chromosomal syndromes having Oro-facial manifestations and mental disabilities’ outlines the main features and clinical symptoms of numerous chromosomal disorders, the main focus being the oral treatment, approach and management of these patients by dentists. The two most commonly used methods, conscious sedation and general anaesthesia are discussed in depth, specifically in the UK and USA. This thesis highlights those patients with chromosomal disorders pertaining to behavioural and mental difficulties. Aside from the physical symptoms that require treatment, it is an important factor to consider the communication and cooperative barriers that dentists and other healthcare professionals may face during treatment, therefore it is necessary to take up the correct measures to facilitate treatment. Being in contact and treating patients with special needs entails many stages of planning and evaluation, from; scheduling appointments for treatments at an appropriate time to allow time for recovery, ensuring a comprehensive and up-to-date medical and dental history is taken by the appropriate healthcare team and establishing good communication. This thesis details the protocol and steps required to accomplish conscious sedation and general anaesthesia in order to safely carry out treatment.