The isolation and storage of platelet concentrates can be accompanied by platelets activation and apoptosis, which cause membrane vesicles release and decline in therapeutic properties of concentrates. However, the mechanisms for the regulation of platelet apoptosis as well as the molecular composition of platelet membrane vesicles remain poorly understood. The aim of the study was to analyze the levels of pro-apoptotic caspase-3 and anti-apoptotic microRNA-221 in platelets and platelet membrane vesicles during storage of platelet concentrates. The object of the study was samples of the pooled platelet concentrates (n = 6), collected from the containers on the 2nd and the 7th day of storage. Full length and activated caspase-3 were found in platelets and in fractions of membrane vesicles. The proportion of activated caspase-3 in platelets increased during storage. MicroRNA-221 was found in platelets, fractions of membrane vesicles, as well as in the extravesicular fraction. During storage, levels of microRNA-221 increased 8-fold (Ð = 0.004) in the fraction of membrane vesicles pelleted at 100 000 g. The results of the work indicate that the membrane vesicles, released by platelets during storage, carry the mature microRNA-221 and the activated form of caspase-3.