  Circumstellar discs are expected to be the nursery of planets. Grain growth
within such discs is the first step in the planet formation process in the
core-accretion gas-capture scenario. We aim at providing selected criteria on
observational quantities derived from multi-wavelength imaging observations
that allow to identify dust grain growth and settling. We define a wide-ranged
parameter space of discs in various states of their evolution. Using a
parametrised model set-up and radiative transfer techniques we compute
multi-wavelength images of discs at different inclinations. Using millimetre
and sub-millimetre images we are in the position to constrain the process of
dust grain growth and sedimentation. However, the degeneracy between parameters
prohibit the same achievement using near- to mid-infrared images. Using face-on
observations in the N and Q Band, the sedimentation height can be constrained.
