The molecular adsorption of benzene on the Si(111)-(7 x 7) surface has bern studied using a combination of semi-empirical (PM3) and density functional theory (DFT) (pBP86/DN--) methods with cluster models. Two di-sigma bonded adsorption configurations corresponding to the 1,2 and 1,4 states are considered. Energy calculations by both theoretical methods have revealed that the 1,4 state is thermodynamically favoured over the 1,2 state. In particular, the adsorption energy and vibrational frequencies of the 1,4 state predicted by the DFT method are in excellent agreement with the experimental observations, which further confirms the 1,4-cyclohexadiene-like binding state of benzene on Si(111)-(7 x 7).