The interactions between dietary fiber (DF)-bound antioxidants and free antioxidants, with different substitution patterns of –OH and –OCH₃ groups on their aromatic rings has been investigated. The activity and efficiency of these interactions were examined with a structural approach. Whole wheat (WW) DF-bound antioxidants and 21 hydroxycinnamic acid/hydroxybenzoic acids (HCA/HBA) were used in the experimental studies. Studies were performed in liposome and aqueous media by monitoring lipid oxidation and scavenging of DPPH radical in the presence of WW-bound antioxidants and HCA/HBA derivatives. Predominantly synergistic interactions were observed in aqueous medium, while both synergistic and antagonistic interactions were seen in liposome medium. Concentrations of HCA/HBA and WW-bound antioxidants in mixtures and their 2-way interactions made significant effect on lipid oxidation and radical scavenging reactions, with some exceptions. HCA/HBA derivatives with 3,4 -dihydroxyphenyl substitution acted as strong antioxidants in liposome medium, while the number of –OH groups affected antioxidant activity in aqueous medium.