Functional components which are stationarily mounted in a fuel tank and connected together by way of a connecting line can be damaged by a change in size and shape of the fuel tank. The invention concerns a fuel tank, in particular of thermoplastic material, comprising at least two functional components such as for example venting valves, pumps, containers or the like, which are stationarily arranged in a fuel tank and which are connected together by way of a connecting line. To avoid damage, in accordance with the invention one connecting line includes at least a first portion and a second portion, wherein the stiffness of the first portion is less than the stiffness of the second portion.