  We analyze the exclusive rare $B \to K^{(*)} \ell^+ \ell^-$, $B \to K^{(*)}
\nu \bar \nu$ and $B \to K^* \gamma$ decays in the Applequist-Cheng-Dobrescu
model, an extension of the Standard Model in presence of universal extra
dimensions. In the case of a single universal extra dimension, we study the
dependence of several observables on the compactification parameter 1/R, and
discuss whether the hadronic uncertainty due to the form factors obscures or
not such a dependence. We find that, using present data, it is possible in many
cases to put a sensible lower bound to 1/R, the most stringent one coming from
$B \to K^* \gamma$.
