Leukocyte differential count in peripheral blood smear has, ever since the method was developed more than 100 years ago, been one of the most frequently used diagnostics tool in the routine hematology laboratory. The manual differential count of leukocytes using a microscope is still the standard method in most small and medium sized laboratories. Even though the method does not require any expensive instruments it comes at a high cost due to it being labor intensive and time consuming. In recent years the rapid technical advancements has led to the development of automatic or semi-automatic methods in which the leukocytes are differentiated. In this study a method comparison was made between manual leukocyte differential counts, CellaVision DM1200 Vet and Advia 2120 when analyzing 106 fresh, feline blood samples. The general agreement between results was good, especially for the most common leukocytes, such as neutrophils and lymphocytes. Results for eosinophils and monocytes had moderate agreement. The confidence intervals were generally wider when CellaVision DM1200 Vet was compared with Advia 2120, than when CellaVision DM1200 Vet was compared to the manual differential count. Despite the fact that Advia 2120 and CellaVision DM1200 Vet are both faster and often show comparable results to the manual differential count, the light microscopy will remain the gold standard for difficult samples, where there is suspicion of inflammation (band neutrophils), intracellular microorganisms, reactive lymphocytes or if the sample contains a high degree of smudge cells or artifacts.