  By adapting some ideas of M. Ledoux \cite{ledoux2}, \cite{ledoux-stflour} and
\cite{Led} to a sub-Riemannian framework we study Sobolev, Poincar\'e and
isoperimetric inequalities associated to subelliptic diffusion operators that
satisfy the generalized curvature dimension inequality that was introduced by
F. Baudoin and N. Garofalo in \cite{Bau2}. Our results apply in particular on
all CR Sasakian manifolds whose horizontal Webster-Tanaka-Ricci curvature is
non negative, all Carnot groups with step two, and wide subclasses of principal
bundles over Riemannian manifolds whose Ricci curvature is non negative.
