The electrochemical reduction of CO2 represents a promising alternative for obtaining a variety of useful products, with important applications in chemical industry or for power generation. However, finding an effective electrode for the activation and further reduction of CO2 continues to be a key challenge. In addition, the reaction mechanism of the process and the involved intermediates are not fully clear as most works analyze the electrolysis products after CO2 reduction reaction, sampling the compounds in gas collectors or liquid solvents. With the main aim of generating knowledge, in situ techniques have been also used for the identification of the electrolysis products from CO2 reduction. Although these techniques are powerful tools for the elucidation of the reaction pathways, they are not commercial or recently introduced into the market, and are not easy to use and, hence, these methods have not been widely employed. In the current chapter a review of the most commonly in situ techniques used for studying CO2 electroreduction is addressed, paying special attention to the electrodes involved in the reaction. Furthermore, an explanation of the main experimental specifications is also described for an easier understanding of the method and a comparison of the in situ techniques, summarizing their advantages and disadvantages, is given.