Surface-enhanced Raman scattering (SERS) was used to study the photochromic behaviour of 3,3-diphenyl-naphtho[2,1-b]pyran in acetonitrile solutions at room temperature. Analysis of SERS spectra of irradiated solutions (UV, UV + visible) has allowed us to separate the spectral contribution of the different photoproducts involved during the photochemical reaction and during thermal relaxation. These experiments demonstrate that, under successive UV and visible irradiation, a new species A is accumulated and then relaxes to the initial closed form (CF), via the TC photomerocyanine isomer. The SERS spectrum of A displays several analogies with the spectrum of CF and this indicates that the structure of A is near to the closed form, with no conjugation between phenyls and naphthalene moiety. On the basis of similar recent NMR experiments, it is suggested that A could be an allenyl-naphthol derivative.