In this work we present a theoretical model that takes into account the impact of loss in the generation of photon-pairs through the four-wave mixing process in a highly nonlinear waveguide. Moreover, we also include in the theoretical model the Raman scattering that occurs inside that waveguide. Results indicate that, the bandwidth over which we can efficiently generate correlated photon-pairs is limited by both the phase-matching condition and the Raman scattering process. Results indicate that, in a non-negligible loss regime the presence of the loss coefficient tends to improve the degree of correlation between the photon-pairs generated inside the waveguide.