Using spectrophotometric method, it be came possible to establish the formation of complex compounds between cobalt(II) and 1-oxi-2-nafthoic acid (1,2-ONA) in the presence of 2,2’-dipyridil (2,2’-Dipy) in acid medium. Correlation between Co:ONA:Dipy = 1:2:1 components, stability of complex (lgβK=26,80), molar coefficient of absorption (ε=2,04.104), form of ion-coordinating metal and the number of proton displaced have been determined. Methods of cobalt determination worked out.