The presence of air between the visceral pleura and the parietal pleura with consecutive retraction of the lung from the chest wall is called pneumothorax. Regarding the genesis of the pneumothorax, a distinction is drawn between spontaneous and traumatic pneumothorax. The spontaneous pneumothorax is, depending on whether a congenital or an acquired pulmonary disease can be found, grouped into a primary spontaneous pneumothorax (PSP) without underlying lung disease and a secondary spontaneous pneumothorax (SSP) with the presence of a known lung disease. The traumatic pneumothorax is classified, depending on the cause, into penetrating and non-penetrating (blunt) traumatic events. A special form of the traumatic pneumothorax is the iatrogenic pneumothorax occurring as a result of diagnostic and/or therapeutic interventions. Clinically, a pneumothorax can range from an asymptomatic to an acute life-threatening situation. The required initial measures depend primarily on the patient's clinical condition. They vary from immediate insertion of a chest tube to wait and see with monitoring. The insertion of a chest tube is still the accepted therapeutic standard, but other procedures like aspiration of air through a needle or small catheter, particularly for small spontaneous pneumothoraces, represent alternative therapy options as well. The short-term goal is to treat possibly existing dyspnea and pain; in the long run a recurrence of the pneumothorax should be prevented. Until now, no uniform treatment algorithms or standardised therapy principles exist to achieve the therapeutic intentions of lung expansion and freedom from pain and late relapse.