In the last several decades, antioxidants have become frequent subject of scientific investigations due to their role in oxidative stress and aetiology of various diseases. Antioxidants include a broad spectrum of mono- and polyphenolic compounds, such as phenolic acids, and also a significant number of synthetic polyphenolic compounds. In this work, an overview of theoretical research on antioxidant potential of selected phenolic acids was given. Adequate thermodynamic parameters which play the key role in selected mechanisms of antioxidant activity were also studied and a conclusion regarding antioxidant potential was drawn from this study. Additionally, results of studies of reactions of phenolic acids with free radicals were presented, and studied mechanisms were HAT, SET-PT, SPLET and RAF, in polar and non-polar medium. Based on the results of computed parameters, possible and competitive mechanisms were determined, as well as phenolic acids with higher antioxidant potential. This activity plays an important role in fighting against various chronic and age-related diseases, such as cardiovascular, neurodegenerative and some types of cancer.