The electronic structures of quasi-one-dimensional halogen-bridged mixed-metal compounds [Ni1-xPdx(chxn)(2)Br]Br-2 were investigated by means of powder X-ray diffraction measurements. Unit cell lengths of all directions obeyed a linear relationship when x < 0.9, whereas those deviated when x > 0.9 especially in the case of the b and c axes. This deviation can be explained by a phase change from an M-III Mott-Hubbard state to an M-II-M-IV charge-density-wave state because of chemical pressure caused by the substitution of Pd ions into [Pd(chxn)(2)Br]Br-2 with smaller Ni ions.