  C-theory provides a unified framework to study metric, metric-affine and more
general theories of gravity. In the vacuum weak-field limit of these theories,
the parameterized post-Newtonian (PPN) parameters $\beta$ and $\gamma$ can
differ from their general relativistic values. However, there are several
classes of models featuring long-distance modifications of gravity but
nevertheless passing the Solar system tests. Here it is shown how to compute
the PPN parameters in C-theories and also in nonminimally coupled curvature
theories, correcting previous results in the literature for the latter.
