The paper deals with a theoretical description and application of electrohydrodynamic impedance. The problem solution comprises three steps. These are an analysis of hydrodynamic conditions (step1), an analysis of mass transfer (step2) , and an analysis of the kinetics (step3). The theory is illustrated by applications in most diverse fields of electrochemistry : electrocrystallization, anodic dissolution of metals, corrosion processes, modified electrodes, passive layers determination of molecular diffusion coefficients, etc.