There is provided a cap and socket arrangement for compact fluorescent lamps. The lamp comprises a discharge tube arrangement made of glass and having sealed ends being positioned at one end of the lamp. A continuous arc path is formed inside the discharge tube between two electrodes disposed at one end of the lamp. At least one of the sealed ends is also provided with an amalgam fill. The sealed ends of the discharge tube arrangement are received in the cap, and the cap comprises contact members and a protruding fitting member for being received in the socket. The socket has a hollow member for receiving the fitting member of the cap, and contact elements for receiving the contact members of the cap. The fitting member and the socket are provided with matching positioning elements for determining the position of the cap with respect to the socket and thereby determining the spatial position of the electrode with respect to the amalgam. The fitting member of the cap of the lamp may comprise an asymmetric groove and the socket may be provided with an asymmetric key element to be associated with the asymmetric groove of the cap.