Objective:Describe the histological and cancer frequency in children and adolescents attended at the Hospital de Base Dr. Ary Pinheiro and the Hospital de Barretos / Rondônia, Western Amazonia, in the years 2014 and 2015. Method: This is a descriptive, quantitative and transverse study. We used a structured instrument containing a series of variables, such as gender, age, histological types, more frequent neoplasms, lymphomas, leukemias, among others. We asked The Comitê de Ética em Pesquisa em Seres Humanos (Research Ethics Committee) to dispense the Informed Consent Form because the study did not require intervention on the patient or collection of biological material, and no possibility of constraints on patients and their relatives. Results: From 75 cases, 32 (42.7%) were female and 43 (57.3%) were male. Regarding the distribution of patients according to the age group, 21 (28.0%) were younger than 4 years, 12 (16.0%), 5 to 9 years, 17 (22.6%) from 10 to 14 and 25 (33.4%) from 15 to 19. The most frequent histological types by gender were leukemias of myeloproliferative diseases and myelodysplastic diseases with 30% and 50% new cases in the period, followed by lymphomas and reticuloendothelial neoplasms with 16.65% and 20, 0% of the histological types in the period. Leukemia in the hematopoietic and reticuloendothelial system (C42) is the most frequent cancer in both, female and male gender, with 47.5% of cancers in the biennium. The second group of cancers in children from 0 to 19 years old and location of the primary tumor is the encephalon carcinoma (C71), with 11.25% of the new cases. Conclusions: The results presented with their proper nuances are in agreement with the data of studies carried out in Brazil and in other countries