Tension pneurnothorax can be associated with several disease conditions such as bacterial pneumonia, pulmonary abscesses, dirofilariasis, pulmonary neoplasia, emphysema, rupture of pulmonary blebs and bullae, fissures of the visceral pleura or chest trauma. In these cases, air accumulation in the pleural space is continuous, so intermittent suction is not a good therapeutic option. Evacuation of air by means of continuous thoracic suction is the treatment of choice, although it is not commonly performed in veterinary practice in our country. In this paper we describe two cases presented to the Veterinary Teaching Hospital of the Complutense University with tension pneurnothorax. The first one had open wounds in the chest and the second one developed pneurnothorax following thoracic surgery. After repeated intermittent chest drainages, pneurnothorax developed again in both patients, leading us to perform continuous thoracic suction using a chest tube connected to a double seal chest drainage unit. Both patients showed a positive recovery and were discharged 72 h and 96 h after beginning the suction, respectively.