Ovine pulmonary adenocarcinoma (OPA) and Small ruminant lentivirus (SRLV) infection are debilitating, progressive and longstanding diseases, associated to high economic losses in livestock farms. These two diseases can coexist in an animal inflicting among other injuries serious lung disease. The possibility of synergism between the two agents has been speculated for several authors. Due to the lack of serological tests for OPA early diagnosis, the use of imaging techniques (e.g. ultrasound examination) is recommended. Confirmation of the diagnosis includes histopathological and molecular techniques. The main aim of this work was characterizing pulmonary lesions of OPA and SRLV coexisting infections using imaging and pathological diagnostic techniques.