A high-frequency filter with at least one coaxial resonator having the following features: - the coaxial resonator includes an outer conductor housing to form an outer conductor, - an inner conductor is disposed in the outer conductor housing, which inner conductor is on its one side mechanically and galvanically connected to the outer conductor housing and terminates on its side opposite the outer conductor housing or spaced from a housing cover provided at, and associated with, the outer conductor housing, - the outer conductor housing and the inner conductor consist of, or are coated with, an electrically conductive material, - the inner conductor comprises an end face and a further surface adjacent thereto, wherein the end face and the further surface adjacent thereto are fully or partially covered with a sheathing material - the sheathing material consists of a dielectric material, and - the dielectric material has a dielectric constant er that is greater than 1.2, - the thickness of the sheathing material is at least 0.05 mm, and less than 3 mm. characterized by the following further features: - the sheathing material consists of, or includes, a dielectric material in the form of one or several cyclic olefin copolymers and - the sheating material is a) opposite the lower side of the housing cover and spaced from the inner side of the outer conductor or b) provided with at least one or preferably with several supports that extend from the sheathing material in axial and/or radial direction and that are preferably elastically supported on the inner wall of the outer conductor housing and/or of the housing cover. - the coaxial resonator includes an outer conductor housing to form an outer conductor, - an inner conductor is disposed in the outer conductor housing, which inner conductor is on its one side mechanically and galvanically connected to the outer conductor housing and terminates on its side opposite the outer conductor housing or spaced from a housing cover provided at, and associated with, the outer conductor housing, - the outer conductor housing and the inner conductor consist of, or are coated with, an electrically conductive material, - the inner conductor comprises an end face and a further surface adjacent thereto, wherein the end face and the further surface adjacent thereto are fully or partially covered with a sheathing material - the sheathing material consists of a dielectric material, and - the dielectric material has a dielectric constant er that is greater than 1.2, - the thickness of the sheathing material is at least 0.05 mm, and less than 3 mm. characterized by the following further features: - the sheathing material consists of, or includes, a dielectric material in the form of one or several cyclic olefin copolymers and - the sheating material is a) opposite the lower side of the housing cover and spaced from the inner side of the outer conductor or b) provided with at least one or preferably with several supports that extend from the sheathing material in axial and/or radial direction and that are preferably elastically supported on the inner wall of the outer conductor housing and/or of the housing cover. a) opposite the lower side of the housing cover and spaced from the inner side of the outer conductor or b) provided with at least one or preferably with several supports that extend from the sheathing material in axial and/or radial direction and that are preferably elastically supported on the inner wall of the outer conductor housing and/or of the housing cover.