  In braneworld models coming from string theory one generally encounters
massless scalar degrees of freedom -moduli- parameterizing the volume of small
compact extra-dimensions. Here we discuss the effects of such moduli on
Newton's law for a fairly general 5-D supersymmetric braneworld scenario with a
bulk scalar field $\phi$. We show that the Newtonian potential describing the
gravitational interaction between two bodies localized on the visible brane
picks up a non-trivial contribution at short distances that depends on the
shape of the superpotential $W(\phi)$ of the theory. In particular, we compute
this contribution for dilatonic braneworld scenarios $W(\phi) = e^{\alpha
\phi}$ (where $\alpha$ is a constant) and discuss the particular case of 5-D
Heterotic M-theory.
