In contrast to the impact and bonding mechanisms in cold spraying, the topic of size effects in the deformation of ceramic particles, as in aerosol deposition, is far from being fully understood. The only established principle of aerosol deposition is that there are deformation mechanisms that allow plastic-like deformation in small particle sizes, typically smaller than one micron. It is also not clear to which extent and in what way the size-related hardening effects could play a role in this deformable regime. With the aim of supplying possible recipes for powder development, two-dimensional molecular dynamics (MD) simulations are applied to study the effect of size on the impact and bonding behaviour of TiO2. nanoparticles. The nanoparticles are assumed to have the original size of 10-50 nm and impact the substrate at velocities of 100-800 m/s. The applied Lennard-Jones potential for the modelled nanoparticles were adjusted to mimic the mechanical properties of TiO2-anatase. The simulations reveal that the intrinsically brittle nanoparticles show three different impact behaviours of (i) rebounding, (ii) bonding and (iii) fragmentation, based on their initial size and impact velocity. The different impact behaviours were analysed in detail by mapping the evolution of the stress and strain fields. The results show that smaller particles start to bond to the substrate at higher impact velocities than the larger ones. Similarly, the smaller particles start to fracture at higher impact velocities. The study suggests that aerosol deposition may need very well-tuned powder size and spray parameter sets for each material, for successful deposition of ceramic coatings. Keywords: aerosol deposition, size effect, molecular dynamics, TiO2, nanoparticle