ABSTRACT: Background MicroRNAs are important regulators of transcription in hematopoiesis. Their expression deregulations were described in association with pathogenesis of some hematological malignancies. This study provides integrated microRNA expression profiling at different phases of chronic myeloid leukemia (CML) with the aim to select CML specific miRNAs and find new possible biomarkers. The functions of in silico filtered targets are in this report annotated and discussed in relation to CML pathogenesis. Results Using microarrays we identified differential expression profiles of 49 miRNAs in CML patients at diagnosis, in hematological relapse, therapy failure, blast crisis and major molecular response. The expression deregulation of miR-150, miR-20a, miR-17, miR-19a, miR-103, miR-144, miR-155, miR-181a, miR-221 and miR-222 in CML was confirmed by real-time quantitative PCR and in silico analyses identified targeted genes of these miRNAs encoding proteins that are involved in cell cycle, growth inhibition, MAPK, ErBb, transforming growth factor beta and p53 signaling pathways that are related to CML. Validated miR-150 decreased levels were detected in patients at diagnosis, in blast crisis and 67% of hematological relapses and showed significant negative correlation with miR-150 proved target MYB and with BCR-ABL transcript level. Conclusions This study revealed microRNAs that may be related to the CML pathogenesis and may reflect transformation from chronic to accelerated phases. The obtained expression patterns in peripheral blood total leukocytes during the course of CML suggest specific miRNAs as possible biomarkers. The annotated functions of in silico filtered targets of selected miRNAs outline mechanisms whereby microRNAs may be involved in CML pathogenesis. Twenty four patient samples of total leukocytes from peripheral blood were used to prepare pools representing different CML phases for microarray analysis: diagnosis (n=5, Dg), major molecular response (n=5, MMR), therapy failure (n=5, TF), hematological relapse (n=5, Hr), and blast crisis (n=4, BC). Eleven healthy donors of age median 60 (range 45 - 78) and man/woman ratio 3/2 following CML incidence were used to create a control pool.