The electrochemical adsorption of thiourea (TU) and urea (U) differs markedly though many physical properties of both compounds are similar. The reason of such behaviour is not quite clear and opinions about the mechanisms of these processes are often controversial. Therefore, the experimental data and thermodynamic parameters of the adsorption of TU and U on mercury electrode from different supporting electrolyte and solvents published in the literature are reviewed and discussed. Also, the results of adsorption of both compounds on different metals, studied by various methods, as well as the influence of the metal structure are presented and commented. The final conclusions are summarized at the end of the review.