Recently, experimental techniques have been developed to map the hot spots and to study the connection between field localization and SHG properties in optical metamaterials.3,4 Since the local field distribution in nanoplasmonic structures is highly inhomogeneous, it is not obvious to establish the role of surface and bulk nonlinearities as well as their relative weights in the overall second harmonic signal. This subject has been investigated, both theoretically and experimentally,5–7 but the relevance of bulk and surface nonlinearities in nanoplasmonic structures is still under debate. Our calculations have been performed by extending to three-dimensional (3-D) structures an algorithm based on the Green’s tensor method, previously developed for calculation of SHG in two-dimensional structures.8,9 With the aim to provide a tool for separating experimental investigation of nonlinear surface and bulk contributions, we studied resonant dipole gold nanoantennas. The SHG as a function of the wire’s cross-section size was investigated in both the near- and far- field regimes, revealing that different geometries and input field polarizations lead to different emission patterns of the second harmonic field. We calculated the second harmonic nonlinear differential scattering cross-section of a antenna when a fundamental frequency field with a wavelength of 800 nm is considered either transverse-electric (TE) or transverse-magnetic (TM) polarized. Our calculations show that there are two different behaviors for the TE and TM pump polarization. Indeed when a TM-polarized pump is considered, bulk terms dominate over surface terms by over one order of magnitude. With a good level of accuracy, the signal generated can be considered as related only to the bulk terms. On the other hand, when surface terms are comparable and/or bigger than bulk contribution (i.e., for TE-polarization, in the considered scheme) the calculated far-field pattern can be very different if both terms are considered with respect to the case where surface terms are neglected. As shown in Fig. 1, the difference is not only in the value of the differential nonlinear scattering cross-section but also in the angular distribution of the generated second harmonic field. By comparing the two plots we can state that the forward generated second harmonic, with respect to the direction of the pump, is related only to the surface terms. These results suggest a way to perform an indirect measurement of the nonlinear coefficient for the bulk and for the surface terms separately.