Two primary malignant lymphomas originating in the right heart cavities have been diagnosed and treated in our department: one, with additional right atrial and inferior vena cava thrombosis required emergency thrombectomy, incomplete excision and chemotherapy and survived 12 years, the other with extensive right ventricular infiltration and failure, died from mediastinitis and aplastic anaemia following surgery and chemotherapy. Quick diagnosis and treatment are indicated. If possible, surgery should be avoided.