A defibrillator for external application to a patient. The defibrillator includes a power storage unit for supplying a defibrillation shock. The power storage unit has a capacitor unit encompassing at least one capacitor. In order to adjust a defibrillation treatment to different patients, the defibrillator advantageously comprises several different capacitor units which have a capacity adapted to various patient impedances and are or can be coupled in a replaceable manner to the defibrillator.
