The aim of this paper is to give a scope of the identification topics currently used in electrochemistry to obtain electrochemical parameters as well as reaction model validation. The paper deals with the close conceptual relationships between basic approaches to the estimation of the frequency response of electrochemical impedance function. The classical methods of frequency and spectral analysis are shown to be the same as the empirical transfer function estimate when periodic signals are used. However, the measurement time depends of what kind of periodical signal is used. The optimal selection criteria of the signal are given in order to obtain minimum measurement time. Studies of the uncertainties on the results using the confidence intervals and qualitative analysis as Kramers-Kronig transform are given. A method to obtain the parameters values from the frequency response of the electrochemical impedance function is given with the computation of model order selection and uncertainties. Finally, an approach to the nonlinear identification of a class of electrochemical system is given.