The substitution of the CO ligand in rhodium(I) β-ketoiminato complexes Rh(R 1 {O,N}R 2 )(CO) 2 ({O,N}=R 1 C(O)CHC(NH)R 2 ; R 1 , R 2 =CF 3 , Me, CMe 3 in several combinations) by phosphorus ligands PZ 3 (PZ 3 =PCy 3 , PPh 3 , P(OPh) 3 , P(NC 4 H 4 ) 3 ) leads to Rh(R 1 {O,N}R 2 )(CO)(PZ 3 ) complexes characterised by 3 1 P{ 1 H}-NMR and X-ray methods. The stronger σ-donor PZ 3 ligands (PZ 3 =PCy 3 , PPh 3 ) substitute almost exclusively the CO group trans to N, forming P-trans-to-N isomers. The complexes Rh(CF 3 {O,N}Me)(CO)(PCy 3 ) (II), Rh(CF 3 {O,N}CMe 3 )(CO)(PCy 3 ) (III), Rh(CF 3 {O,N}Me)(CO)(PPh 3 ) (IV) and Rh(CF 3 {O,N}CMe)(CO)(PPh 3 ) (V) are of a square-planar geometry with a slight tetrahedral distortion around the rhodium atom in II, III and V. The Rh P(PCy 3 ) bonds are slightly longer than the Rh P(PPh 3 ) bonds. The reaction of stoichiometric amounts of the less basic P(OPh) 3 or P(NC 4 H 4 ) 3 ligands leads to the formation of both isomers of the Rh(R 1 {O,N}R 2 )(CO)(P(OPh) 3 ) or Rh(R 1 {O,N}R 2 )(CO)(P(NC 4 H 4 ) 3 ) complex in comparable yields. The Rh P(P(OPh) 3 ) distance (2.195(2) Å) in the isomer of Rh(CF 3 {O,N}CMe 3 )(CO)(P(OPh) 3 ) with P(OPh) 3 coordinated trans to N (VI) is ca. 0.04 Å longer than in the isomer of that complex with P(OPh) 3 coordinated trans to O (VII). The CO substitution in Rh(R 1 {O,N}R 2 )(CO) 2 by PZ 3 ligands (PPh 3 , PCy 3 , P(OPh) 3 ) causes the shortening of the Rh C(CO) bond by ca. 0.04 Å compared to Rh(CF 3 {O,N}Me)(CO) 2 (I), making difficult the coordination of another PZ 3 ligand, especially one with stronger σ-donor properties. The more π-acceptor P(OPh) 3 ligands form bis-phosphito complexes and Rh(CF 3 {O,N}CMe 3 ){P(OPh) 3 } 2 (VIII) exhibits inequivalence of the two P(OPh) 3 ligands in solution ( 3 1 P-NMR) as well as in solid form (X-ray).