ScRhO3 and InRhO3 perovskites were synthesized at a high pressure of 6 GPa and a high temperature of 1500 K. Crystal structures of ScRhO3 and InRhO3 were studied with synchrotron X-ray powder diffraction at 293 and 134 K. ScRhO3 and InRhO3 have a rarely observed monoclinic superstructure of the GdFeO3-type structure (space group P2(1)/n, a = 7.45660 angstrom, b = 7.43524 angstrom, c = 7.52191 angstrom, and beta = 93.2930 degrees for ScRhO3 and a = 7.59020 angstrom, b = 7.58377 angstrom, c = 7.59010 angstrom, and beta = 91.4154 degrees for InRhO3 at 293 K). InRhO3 has pseudo-orthorhombic lattice parameters of a = 10.8658 angstrom, b = 7.5837 angstrom, and c = 10.6006 angstrom. ScRhO3 and InRhO3 are nonmagnetic, and no phase transitions were detected between 2 and 873 K. Crystallographic trends and distortions of ScRhO3, InRhO3, and RRhO3 (R = rare earths, Y, and Bi) are discussed.