Contemporary oncotherapy has improved survival of children with malignant diseases, but chemotherapy and radiotherapy also have deleterious effects. This essay illustrates the effects of chemotherapy and radiotherapy on dentition in children and adolescents. The illustrated abnormalities were seen on panoramic radiographs obtained before, during, and after treatment. Included are examples of hypodontia (partial anodontia), microdontia, altered eruption patterns, and root stunting. Comparison is made with normal dental development (Fig. 1).