OMPLEX formation reactions  involving Cd(II), pyridine -2- carboxylic acid ( picolinic acid, PA) and various biorelevant ligands (L) containing different functional groups are investigated at 25 ºC and I = 0.10 M (NaNO3). The ligands (L) used are amino acids, peptides and DNA constituents. The results showed the formation of Cd(II)-(PA)-(L) complexes  with  amino  acids  and  DNA constituents, peptides  form  both  Cd(II)-(PA)-(L)  complexes  and  the  corresponding deprotonated amide  species  Cd(II)-(PA)-(LH_-1).  The  relative stabilities  of ternary complexes  are compared  with those  of the corresponding  binary  complexes  in  terms  of  ∆ log K  values.  The concentration distribution of the complexes in solution was evaluated.