It was shown that nickel monocarbonyl and noble gas atoms, Ar, Ne, and He combine with the binding energy of 9.55, 3.71, and 5.97 kcal/mol, respectively, at the CCSD(T) level. The fundamental for Ni-C-O bending frequency in Ar-NiCO was estimated as 454.3 cm(-1) which is largely shifted from the corresponding value for NiCO, 418.6 cm(-1). It was discussed whether the experimental fundamentals for NiCO in argon matrix should be attributed to NiCO or Ar-NiCO. (C) 2003 Elsevier B.V. All rights reserved.