A device for electrochemotherapy comprises an electric micro- or nano-capacitor which can be injected in the blood circulation of a human or animal body, including a pyroelectric or piezoelectric layer which can be excited from the outside of the human or animal body, for generating an electric field in the immediate vicinity of a tumor cell, together with the administration of a chemotherapeutic agent. The chemotherapeutic agent may be administered with independent means, but preferably is bound to the outer surface of the microcapacitor and is delivered because of the temperature increase which is generated at the time of the microcapacitor excitation.