Aim. To analyse clinical implications of chromosome 8 trisomy in Ph-negative cells of the bone marrow in patients with chronic myeloid leukemia (CML) treated with inhibitors of tyrosinkinases (ITK). Material and methods. A total of 386 patients with CML (chronic phase - 288, acceleration phase - 77) received imatinib (400-800 mg/day). Because of resistance and/or intolerance some patients were switched to ITK II (nilotinib, dasatinib, bozutinib). This study included 8 CML patients (7 in a chronic phase, 1 in acceleration phase) treated with BCR-ABL ITK inhibitors of the first (imatinib) and the second line (ITK-II). The standard cytogenetic examination, on demand - investigation of the interphase nuclei with FISH, in some cases morphological, cytochemical and histological examinations of the bone marrow were made. Results. The existence of a Ph-negative clone with trisomy of chromosome 8 had no negative effect on the course of the disease. The patients showed a stable hematological and cytogenetic response and no need in changing treatment policy. In long-term follow-up Ph-negative clone with trisomy of the chromosome 8 persisted without a clear trend to rise in most patients. Conclusion. Detection of a Ph-negative clone with chromosome 8 trisomy at early stages suggests parallel existence of Ph-positive and Ph-negative clones. None of the patients had myelodisplasia.