Abstract: p-cumaric acid (PCA) i.e. hydroxycinnamic acid is a one of the major component of lignin. PCA can be found in a wide variety of edible plants including peanuts, beans, tomatoes, carrots, garlic etc. It is also found in wine and vinegar. PCA has strong antioxidant properties and is known to reduce the risk of stomach cancer by reducing the formation of carcinogenic nitrosamines. According to that tha main goal of presente dpaper is to establish the basic properties of PCA complexes with some cyclodextrin. Host-guest complexation with cyclodextrins may be interesting to increase the bioavailability of PCA in functional food product. During the research an on-line complexation of p-cumaric acid  with β-cyclodextrin (CD) and and Randomly Methylated β-cyclodextrin (RMCD) was performed using RP-HPLC system. Due to the complex formation of CD with a guest molecule - PCA a significant changes in retention times of PCA was observed. The investigation was performed as a function of temperature as well as cyclodextrin concentration in liquid phase. As a result apparent formation constant – K_F of PCA/CD and PCA/RMCD were calculated. Based on K_F some thermodynamic properties were obtained including standard enthalpy, standard entropy and free Gibbs energy of host-guest complexation. It was shown that the stoichiometry of the complex in both cases is 1:1 and the complexation is an exothermic process. From the other hand the positive value of Gibbs free energy clearly designate the process as forced one. The increase in temperature influence on Gibbs free energy by means of increase of this parameter. Additionally the differences between CD and RMCD as a hosting agents were shown.