Planar Frequency selective surfaces (FSS) have attracted large attention during the last five decades [1] because of their mechanical and electrical flexibility. FSS are spatial filters that are largely employed in applications like hybrid radomes for radars and antennas where high performance is necessary. The FSS have evolved from simple canonical forms to the complex geometries known today. This evolution has been driven primarily by increasingly stringent performance requirements of recent applications. For these structures, we must consider both the effects related to the frequency that those related to the size of the individual elements. While periodicity impacts firstly on the general reflecting properties of the surface, the shape and the size of the individual element affects its detailed both spatial and frequency filtering behaviour. In particular the frequency response is dictated mainly by the scattering of the incident plane wave by the individual element and attains its maximum at resonance conditions. Accordingly, we mean to investigate whether the same occurs also for non planar surfaces and curved elements, and in particular conical surfaces. The analysis is performed in two steps. First the frequency behaviour of input impedence of the single elements emebedded within a number of similar ones is numerically computed by a commercial code. Both single, radial and circumferential strips conforming a conical shape are considered and compared with a planar and cylindrical structure. Next the FSS behiavour is fully analysed by a numerical code solving the Electric Field Integral Equation [2] for a FSS of finite size made of thin elements.