Platelets are produced in the bone marrow, and along with erythrocytes and leukocytes, are the essential part of the complete blood count. In order to avoid unreliable and inaccurate results due to preanalytical errors (eg. pseudothrombocytopenia), microscopic examination of peripheral blood smears is performed. Microscopic examination of blood smears provides information whether the patient has really low platelet counts or is it a consequence of platelet aggregation. The gold standard for determining the presence of platelet aggregates is light microscopy which is very tedious and time consuming. With technological advancements, digital microscopy has been developed, which enables faster examination of peripheral blood smears. The aim of this thesis was to verify the reliability of platelet count evaluation using digital morphology analyzer Sysmex DI-60 (Sysmex, Kobe, Japan). The presence of platelet clumps in the submenus (WBC, RBC, PLT) of the Sysmex DI-60 analyzer was compared with the presence of platelet aggregates by light microscopy. Also, platelet count obtained by the Fonio method on Sysmex DI-60 was compared to the platelet count obtained on the hematology analyzer Sysmex XN-3100 analyzer. Assessment of the presence of platelet clumps by reviewing all submenus of the Sysmex DI-60 analyzer showed satisfactory agreement and comparable performance. The differences between the Fonio platelet count and the Sysmex XN-3100 method were irrelevant and expected because Fonio is only an approximate platelet count method. Accordingly, it was concluded that Sysmex DI- 60 can be introduced into the routine work of the hematology laboratory for assessment of the presence of platelet clumps and platelet count estimation. However, any doubtful case requires examination of the peripheral blood smear by light microscopy.