Objective: Platelets play a critical role in haemostasis and wound repair through platelet interaction with the vessel wall. Pathologically, platelet activation underlies thrombotic diseases such as stroke and myocardial infarction. Well-defined platelet regulatory factors are nitric oxid, reactive oxygen species (ROS), prostacyclin and cAMP. Intracellular ROS signalling is connected with changes in carbonylation and nitration of platelet proteins. The aim of present work was to identify differences between proteome and secretome of resting and activated blood platelets. Methods: Platelets were activated by three agonists: thrombin, collagen and arachidonic acid. Platelet proteins were separated by 2-DE or by PF2D. Corresponding protein spots were analyzed by MALDI-TOF. Results: We found differences in protein location and concentration profile between proteome and secretome of activated and resting platelets. GP IIb, gelsolin, Rho-GDP inhibitor 2 and vinculin were carbonylated during activation by collagen, thrombin and arachidonic acid. Concentrations of elfin, cofilin, vinculin and Rho-GDP inhibitor 2 were reduced in samples of activated platelets. In secretome we found carbonylated beta chain of fibrinogen in activated platelets. Conclusion: Our results indicate that carbonylation, nitration and phosphorylation signalling cascades are situated in the vicinity of cytoskeletal proteins. The knowledge of biochemical and signalling pathways of healthy platelet proteome and secretome could help to understand mechanisms that underlie platelet activation and thrombotic disease. Acknowledgement: Research was supported by AV[Ccaron]R KAN200670701.