Chronic myeloid leukemia ( CML) is generally diagnosed through findings such as marked leukocytosis at full blood count or splenomegaly at physical examination, while isolated thrombocytosis is not an expected condition. This paper examines hematological values, clinical findings, cytogenetic and molecular genetic data from 3 cases of CML presenting with isolated thrombocytosis. In addition, potentially significant differences between cases of CML presenting with isolated thrombocytosis and typical CML were investigated. No splenomegaly was present in these patients, peripheral leukocyte numbers and formulae were normal, LDH and uric acid levels were lower than in classic CML, while hemoglobin levels were higher. BCR/ABL levels were similar. In terms of CML risk scoring, since the EUTOS scoring system is based solely on peripheral blood basophil percentage and splenic dimension it was not considered appropriate for these patients.