In this study we analysed caspase activation in peripheral blood and bone marrow cells of B-cell chronic lymphocytic leukaemia (B-CLL) exposed to apoptosis both spontaneous and induced via external and internal pathway. We used the method based on detection of activated caspases with FAM-VAD-FMK that is the fluorochrome labelled inhibitor of caspases and flow cytometry technique. We detected the higher rate of apoptosis induced by mitochondrial way in comparison to receptor one that may suggest dominance of this mechanism in B-CLL. We also observed the higher rate of spontaneous and mitochondrial-induced apoptosis in peripheral blood in comparison to bone marrow indicating the differences in apoptosis process depending on cell environment.