  We discuss radiation in theories with scalar fields. Our key observation is
that even in flat spacetime, the radiative fields depend qualitatively on the
coupling of the scalar field to the Ricci scalar: for non-minimally coupled
scalars, the radiative energy density is not positive definite, the radiated
power is not Lorentz invariant and it depends on the derivative of the
acceleration. We explore implications of this observation for radiation in
conformal field theories. First, we find a relation between two coefficients
that characterize radiation, that holds in all the conformal field theories we
consider. Furthermore, we find evidence that for a $1/2$-BPS probe coupled to
${\cal N}=4$ super Yang-Mills, and following an arbitrary trajectory, the
spacetime dependence of the one-point function of the energy-momentum tensor is
independent of the Yang-Mills coupling.
