Laser-ablated Sc atoms and ions react with CO molecules to give primarily, the ScCO, ScCO-, and ScCO+ products, which have been isolated in solid argon and/or neon matrices. Based on isotopic substitution as well as density functional calculations, absorptions at 1834.2 cm(-1) in argon and 1851.4 cm(-1) in neon are assigned to C-O stretching vibrations of the ScCO molecule, 1923.5 cm(-1) in argon and 1962.4 cm(-1) in neon to the ScCO+ cation, and 1732.0 cm(-1) in neon to the ScCO- anion, respectively. Higher carbonyls Sc(CO)(2,3,4) and SC(CO)(2,3)(+) are also produced on annealing. Similar argon matrix experiments with Y give YCO and YCO+.