The properties of the [RhCl(PH₃)(CNMe)₂] and [RhCl₃(PH₃)(CNMe)₂] complexes (relative stability of different isomers, structural features, vibrational frequencies, bond nature, atomic charge distribution, and well as analysis of the MO composition and energies) have been studied by quantum-chemical methods. For the [RhCl(PH₃)(CNMe)₂] complex, the cis isomer is the most stable one; for the [RhCl₃(PH₃)(CNMe)₂] complex, the cis-mer isomer is the most stable one. In the [RhCl(PH ₃)(CNMe)₂] complex, the moderate π back-donation effect is observed. The coordination of C≡NMe to the metal should lead to activation of the ligand in nucleophilic addition and cycloaddition reactions with a normal electron distribution and hinder the electrophilic attack at the N atom of isonitrile.