  For the first time an extensive search for various double beta decay modes of
124Sn and 112Sn has been performed. A total exposure of 43.29 kg.days has been
accumulated. New half-life limits of 124Sn into excited states of 124Te have
been obtained; the lower half-life limit for the first excited 2+ state at
602.7keV is T_1/2 > 3.1 *10^{18}yrs (90 % CL) and for the first excited 0+
state T_1/2 > 7.7 *10^{18}yrs (90 % CL). For the very first time, ground state
and excited state transitions of 112Sn have been experimentally explored. The
obtained half-life limits for ECEC and beta+/EC into the first excited 2+ state
of 112Cd are both T_1/2 >1.4 *10^{18}yrs (90 % CL). A resonance enhancement in
the decay rate for 0nuECEC might be expected for the 0+-state at 1870.9keV due
to degeneracy with the 112Sn ground state. No signal was found resulting in a
lower half-life limit of T_1/2 > 1.6 *10^{18} yrs (90 % CL) for this decay. As
all the excited state searches are based on gamma-lines, all half-life limits
apply for both neutrino and neutrino-less modes. Neutrinoless ground state
transitions were searched for in the ECEC and beta+/EC mode and a limit of
T_1/2 > 1.5 *10^{18} yrs (90 % CL) was obtained for ECEC decays of 112Sn,
whilst the beta+/EC mode results are inconclusive.
