  We study transport through double quantum dots coupled to normal and
superconducting leads, where the Andreev reflection plays a key role in
determining characteristic transport properties. We shall discuss two typical
cases, i.e. double dots with serial or parallel geometry. For the parallel
geometry, the interference of electrons via multiple paths is induced, so that
the transmission probability has Fano-type dip structures which are symmetric
with respect to the Fermi energy. We also investigate the Aharonov-Bohm(AB)
effect for the parallel geometry. In some particular situations, we find that
the general AB period for double dots, 4$\pi$, is reduced to 2$\pi$.
