  We reconstruct B0bar --> Ds-D+ decays using a sample of 449 x 10^6 BBbar
pairs recorded by the Belle experiment, and measure the branching fraction to
be Br(B0bar --> Ds-D+)=[7.5 +- 0.2(stat) +- 0.8(syst) +- 0.8(Br's)] x 10^(-3).
A search for the related decay B0bar --> Ds+Ds- is also performed. Since we
observe no statistically significant signal an upper limit on the branching
fraction is set at 3.6 x 10^(-5) (90% C.L.).
