  Solar System tests give nowadays constraints on the estimated value of the
cosmological constant, which can be accurately derived from different
experiments regarding gravitational redshift, light deflection, gravitational
time-delay and geodesic precession. Assuming that each reasonable theory of
gravitation should satisfy Solar System tests, we use these limits on the
estimated value of the cosmological constant to constrain extended theories of
Gravity, which are nowadays studied as possible theories for cosmological
models and provide viable solutions to the cosmological constant problem and
the explanation of the present acceleration of the Universe. We obtain that the
estimated values, from Solar System tests, for the parameters appearing in the
extended theories of Gravity are orders of magnitude bigger than the values
obtained in the framework of cosmologically relevant theories.
