  Combining Monte Carlo radiative transfer simulations and accurate 2D
bulge/disc decompositions, we present a new study to investigate the effects of
dust attenuation on the apparent structural properties of the disc and bulge of
spiral galaxies. We find that dust affects the results from such decompositions
in ways which cannot be identified when one studies dust effects on bulge and
disc components separately. In particular, the effects of dust in galaxies
hosting pseudo-bulges might be different from those in galaxies hosting
classical bulges, even if their dust content is identical. Confirming previous
results, we find that disc scale lengths are overestimated when dust effects
are important. In addition, we also find that bulge effective radii and Sersic
indices are underestimated. Furthermore, the apparent attenuation of the
integrated disc light is underestimated, whereas the corresponding attenuation
of bulge light is overestimated. Dust effects are more significant for the
bulge parameters, and, combined, they lead to a strong underestimation of the
bulge-to-disc ratio, which can reach a factor of two in the V band, even at
relatively low galaxy inclinations and dust opacities. Nevertheless, it never
reaches factors larger than about three, which corresponds to a factor of two
in bulge-to-total ratio. Such effect can have an impact on studies of the black
hole/bulge scaling relations.
