The goal of the present paper was to establish criteria for the differentiation of thymic lymphoma and haematoma of the ventral neck in cattle. Four cattle with thymic lymphoma and seven with haematoma of the ventral neck underwent physical, haematological, biochemical and ultrasonographic examinations as well as histological evaluation of a biopsy specimen. All of the animals had firm non-painful swellings, which were no warmer than normal and extended from the pharyngeal region to the thoracic inlet. A diagnosis could not be established based on the results of physical examination and palpation of the swellings. Animals with a haematoma had a shorter history of being ill compared to those with thymic lymphoma. In patients with a haematoma, anaemia was present, the heart rate was elevated and the haematocrit was decreased, but not in cattle with thymic lymphoma. A tentative diagnosis was made on the basis of a macroscopic evaluation of the biopsy samples, which were dark red and firm in cattle with a haematoma. All cases of malignant thymic lymphoma were confirmed by histological examination of a biopsy sample. Ultrasonography did not help to differentiate between haematoma and thymic lymphoma. All animals with thymic lymphoma and three of those with a haematoma were euthanased. The four remaining animals with a haematoma were treated successfully.