  We present an axi-symmetric model for the ultraviolet (UV)-to-submillimetre
(submm) images of the nearly face-on spiral galaxy NGC 628. It was calculated
using a radiative transfer (RT) code, accounting for the absorption and
re-emission of starlight by dust in the interstellar medium of this galaxy. The
code incorporates emission from Polycyclic Aromatic Hydrocarbons, anisotropic
scattering and stochastic heating of the grains. This is the second successful
modelling of a face-on spiral galaxy with RT methods, whereby the large-scale
geometry of stars and dust is self-consistently determined. The solution was
obtained by fitting azimuthally averaged profiles in the UV, optical and submm.
The model predicts remarkably well all characteristics of the profiles,
including the increase by a factor of 1.8 of the scale-length of the infrared
emissivity between 70 and 500 $\mu$m. We find that NGC 628 did not undergo an
efficient inside-out disk growth, as predicted by semi-analytical hierarchical
models for galaxy formation. We also find large amounts of dust grains at large
radii, that could involve efficient transport mechanisms from the inner disk.
Our results show that 71% of the dust emission in NGC 628 is powered by the
young stellar populations, with the old stellar populations from the bulge
contributing 65% to the heating of the dust in the central region ($R<0.5$
kpc). The derived star formation rate is $\rm SFR=2.00\pm0.15\,{\rm
M}_{\odot}{\rm yr}^{-1}$..
