This invention relates to an automated cardiopulmonary resuscitation device for cyclically compressing a patient's chest. The CPR device comprises a front structure with a first and a second movable unit arranged to move back and forth along said front structure; a back support for positioning behind the patient's back arranged to keep the front structure in a fixed position relative to the patient's back; a chest pad; two arms each rotatably coupled to the chest pad with one end and each being rotatably coupled to a respective one of the first and the second movable units; and a motor arranged for, when in operation, driving the first and the second movable units back and forth such that the chest pad cyclically compresses the patient's chest.