Laser-ablated Ag and Au atoms have been reacted with CO molecules followed by condensation in excess neon at 4 K. Besides the neutral carbonyls [Ag(CO)(n) (n = 2, 3), Au(CO)(n), (n = 1, 2), Au-2(CO)(2)], the metal carbonyl cations [M(CO)(n)(+) (n = 1-4)] have been formed and identified. The CO concentration, isotopic substitution and CCl4 doping experiments confirm the identification of the cationic species. Excellent agreement between observed bands and frequencies and isotopic frequency ratios from the DFT calculations support the vibrational assignments and identification of the metal carbonyl complexes.