We evaluated the oral health status of 85 acute lymphoblastic leukemia (ALL)/lymphoma pediatric patients who received remission-induction and maintenance chemotherapy and 85 age and sex-matched healthy children with the criteria of World Health Organization (WHO) and to determine the prevalence and distribution of dental problems in order to constitute preventive dentistry precautions in this study. The gingival tissues were scored with Community Index of Periodontal Treatment Necessity (CPITN) and dmf-t and DMF-T indices were used for caries evaluation. In the study group, malocclusion was found in 24 patients (28.2%). CPITN was scored as follows in the study group; 11% of the patients had healthy gingiva (Grade 0), the presence of plaque (Grade I) 79% of the patients, the presence of calculus (Grade II) 10% of patients were observed. Nevertheless, mucositis was found with various grades in 9 patients who received chemotherapy. Decayed teeth were found in the 76 patients and in 45 healthy children. 91.7% of patients and 52.9% of children needed dental treatment were determined. The DMF-T and dmf-t scores showed that ALL/lymphoma patients had more decayed and needed more dental treatment, missing or filled teeth both in their deciduous (p< 0.001) and permanent (p< 0.05) dentition when compared to systemically healthy children.