Oral manifestations are often present in all types of leukaemia, and are particularly severe in children. Oral diseases may result as complications of aggressive cytotoxic therapy. On the other hand, oral diseases that are already present in the oral cavity could be aggravating the patient's general condition and lead to serious life-threatening infections. The aim of this paper was to highlight the importance of preventive measures in maintaining oral health, as well the measures for controlling oral disorders onset during the course of illness and applied therapy in children with acute leukaemia. All preventive measures that include proper, regular hygiene and intervention depend on the patient's haematological status and general health condition, and are performed with the consultation and approval of the haematologists-in-charge. The preventive program can be implicated in three stages; before the beginning of cytotoxic therapy, during active cytotoxic therapy and after cytotoxic therapy. Having in mind that oral disease can influence general treatment in children with acute leukaemia dramatically, developing protocols on the implementation of all measures of oral prevention and treatment is mandatory.