Surface-enhanced Raman (SER) scattering of 2-cyanonaphthalene (2-CN) has been investigated in silver sol. Addition of halide ions was needed to obtain authentic SER spectra of the molecule. The SER spectra thus obtained exhibited a slight but noticeable dependence on the kind of halide ions used. This halide-dependent spectral variation was attributed to the orientational change of molecule on silver sol surface. A possible mechanism for such an orientational change is proposed in terms of the competitive adsorption of 2-CN with halide ions on the so-called halide-specific sites.