The reliability of complete blood counts (CBC) obtained by LaserCyte® were evaluated in 41 dogs affected by malignant lymphoma (29 cases), leukemia (8 cases) and miscellaneous blood disorders (4 cases). A total of 89 CBCs were performed. Different degrees of anemia, leukocytosis, leucopenia and thrombocytopenia or thrombocytosis were detected. Results provided from LaserCyte® were compared with those from HeCo VET C® impedance cell counter, manual leukocyte differential counts and reticulocyte counts by the regression coefficient (r). The LaserCyte® cell counter provides reliable results for diagnosing and monitoring onco-hematological disorders, in part due to the provision of alarm codes that indicate when a review of the stained blood smear is necessary. The only unreliable CBC parameter was eosinophil count.