The total number of hemocytes and their morphological characteristics were analyzed in Helix pomatia Linnaeus, 1758, by light microscopy during different phases of hibernation. Three types of hemocytes were identified: hyalinocytes, agranulocytes, and granulocytes. Total number of hemocytes decreased significantly during hibernation. Most intensive changes in cell size, morphology, and appearance of special structures in granulocytes happened during the hibernation period itself. Termination of hibernation coincides with very important granulocyte transformation and the appearance of specific gigantic short-lived cells. All of the changes in cell number and morphology are characteristics of different hibernation phases and have a major role in adaptive hypothermia. Granulocytes are hemocytes of great importance in immune response while specific functions of hyalinocytes and agranulocytes remain largely unexplored.