Abstract: Molecularly imprinted polymers (MIPs) are a class of highly cross-linked polymer that can bind certain target compound with high specificity. The polymers are prepared in the presence of the target molecule itself as the template. The template interacts with functional monomers before being cross-linked in polymerization process. The specific binding site complementary to the target analyte is generated upon the removal of the template from the solid polymers. The knowledge of the interactions between the target (in this case, cocaine and benzoylecgonine molecules) and the monomer seems to be very important in the design of this MIPs. For this reason, a computational study of the interactions between cocaine and benzoylecgonine molecules, and methacrylic acid is presented. Different position for the interactions and number of molecules of monomer are considered in this DFT study. The effect of solvent is also analyzed.