  In the context of $f(R)$ theories of gravity, we address the problem of
finding static and spherically symmetric black hole solutions. Several aspects
of constant curvature solutions with and without electric charge are discussed.
We also study the general case (without imposing constant curvature). Following
a perturbative approach around the Einstein-Hilbert action, it is found that
only solutions of the Schwarzschild-(anti) de Sitter type are present up to
second order in perturbations. Explicit expressions for the effective
cosmological constant are obtained in terms of the $f(R)$ function. Finally, we
have considered the thermodynamics of black holes in anti-de Sitter space-time
and found that this kind of solutions can only exist provided the theory
satisfies $R_0+f(R_0)<0$. Interestingly, this expression is related to the
condition which guarantees the positivity of the effective Newton's constant in
this type of theories. In addition, it also ensures that the thermodynamical
properties in $f(R)$ gravities are qualitatively similar to those of standard
General Relativity.
