The application relates to a device for an intermittent or continuous administration of a therapeutical substance, such as insulin, comprising an injection part and a fluid delivery part (3,4). The fluid delivery part normally comprises a reservoir (4), transferal means e.g. in form of a pump and a house (3), and the injection part normally comprises a base plate (10), a cannula part (1,16) comprising a cannula (9) extending past the proximal side of the base plate and means for fixation of the base plate to the skin of the user. According to the application the device comprises a base plate (10), a cannula part (1, 1b) comprising a body providing a through-going opening leading liquid to a cannula (9) which cannula (9) extends past the proximal side of the base plate (10) and means (21) for fixation of the base plate to the skin of the user wherein a flexible part is arranged in an area between the subcutaneously positioned section of the cannula (9) and the fluid delivery part (3, 4).