  The dynamics of test particles in $f(\mathcal G)$ modified Gauss-Bonnet
gravity is investigated. It is shown that in $f({\mathcal G})$ gravity models
with non-minimal coupling to matter, particles experience an extra force normal
to their four-velocities and as a result move along non- geodesic world-lines.
The explicit form of the extra force depends on the function of the
Gauss-Bonnet term included in coupling term. The effects of this force on the
relative accelerations of particles are studied.
