In his or her practice, every dentist encounteres oncology patients of all ages, including children with different malignant diseases. Doctors of dental medicine must have basic knowledge of cancer genetics, the most common types of childhood cancer, types of cancer therapy and oral complications to provide the best possible care for these patients, who require special approach and attention. The role of evey dentist is to prevent complications when is possible to prevent, to alleviate complications that occur during the therpy and to know which dental procedures are risky for different kind of patients and different stages of disease. Considering that we work with pediatric patients, we must include the parents in each procedure and explain to them what they can expect during different stages of cancer therapy. During this difficult life periods for children and parents, we must show understanding for them and have special psychological approach. Children develop accute complications that withdraw within several weeks after completing the therapy. Those complications are: oral mucositis, secundary infections, taste changes and xerostomia. Chronic complications are: radiation caries, trismus, osteoradionecrosis and chronic Graftversus-Host Disease. Oral complications that are specific for children are distrubances in craniofacial and dental development, and dental anomalies. These complications are result of harmful effects that radiation and cytostatic drugs have on children and their develompent.