The most common childhood neoplasms are leukemia, brain and spinal cord tumors, and lymphomas. Acute lymphoblastic leukemia is the most common malignancy since the second year of life, and lymphomas, bone tumors, and gonadal tumors occur more frequently after the age of ten. About 150 children get sick every year in the Republic of Croatia. Treatment is complex, involves the work of a multidisciplinary medical team, and often leaves lasting physical, as well as psychological consequences for the health of the sick. Although tumor treatment methods in children are aggressive, with numerous side effects and late sequelae, about 75-80% of diseased children survive today. The aim of this paper is to present the characteristics of malignant diseases in childhood, their treatment and consequences of treatment, psychosocial effect of the disease on the child and parents, palliative care for terminally ill child and the role of the nurse in the treatment and care of the sick child.