Sm2MnMn(Mn4-xTix)O-12 with 1 <= x <= 3 were prepared by a high-pressure, high-temperature method at 6 GPa and about 1570-1670 K. They belong to a family of A-site columnar-ordered quadruple perovskites A(2)A'A '' B4O12, where A' is a site with a square-planar coordination and A '' is a site with a tetrahedral coordination. Their crystal structures were investigated using synchrotron X-ray and neutron powder diffraction. They crystallize in space group P4(2)/nmc (No. 137) with a = 7.41172 angstrom and c = 7.97131 angstrom for x = 1, a = 7.54945 angstrom and c = 7.76756 angstrom for x = 2, and a = 7.63949 angstrom and c = 7.70339 angstrom for x = 3 at 295 K. The determined charge and cation distributions are [Sm1.883+Mn0.122+](A)[Mn3+](A')[Mn0.882+Sm0.123+](A '')[Mn33+Ti4+](B)O-12 for x = 1, [Sm1.913+Mn0.092+](A)[Mn2+](A')[Mn0.912+Sm0.093+](A '')[Mn23+Ti24+](B)O-12 for x = 2, and [Sm1.883+Mn0.122+](A)[Mn0.882+Sm0.123+](A')[Mn2+](A '')[Mn2+Ti34+](B)O-12 for x = 3. Mn and Ti are distributed randomly in one B site in all compounds with the average oxidation state changing from +3.25 to +3.5 per one B atom, and such flexibility is realized because Mn at the A' site can change its oxidation state between +2 and +3. Sm and Mn are slightly disordered between the A and A '' sites for x = 1 and 2, and between the A and A' sites for x = 3. The x = 1 sample shows spin-canted antiferromagnetic properties with T-N = 27 K, and the x = 2 sample, with T-N = 62 K. On the other hand, the x = 3 sample is a ferrimagnet, confirmed by neutron diffraction, with T-C = 40 K. The x = 3 sample shows relaxor-like dielectric properties below 220 K.