Subdural hematoma (SDH) develops as a result of bleeding in the subdural space. According to nowadays accepted division, three groups of subdural hematomas can be differentiated: acute, subacute and chronic. The time elapsed from the moment of the occurrence of the hematoma to the moment when it was diagnosed is the main factor for determining the stage of SDH. However, for the above-mentioned types of SDH, this time differs depending on the author reporting it. Subdural hematoma is most often diagnosed by means of computerized tomography (CT). This method is safe and reliable, giving the exact diagnosis in more than 90% of cases. According to the basic principle of the concept of "living pathology", the knowledge of histological appearance of an investigated lesion is essential for the diagnostic interpretation of this lesion in neuroimaging methods. Very few authors studied the histological picture of subdural hematoma. The only structure which was histologically examined in details was the subdural neomembrane. Studies correlating histological picture of SDH and its appearance on CT scans have not been carried out until now. In this work such a correlation was made, and some regularities connecting these two methods were pointed out. Hyperdense picture of SDH on CT scans represents a hematoma containing almost only erythrocytes and erythrocyte-fibrin component being formed. Hypodense picture of SDH on CT scans represents a hematoma containing fibrin and inflammatory cells. Hematomas of mixed density on CT scan in all cases contained a neomembrane. Obvious histological differences between the mentioned types of subdural hematoma have led to the conclusion that chronic subdural hematoma is not the last stage of an "old" acute SDH. Chronic and acute subdural hematomas are different entities, considering their etiopathogenetic and clinical picture, and especially their CT and histopathological appearances.