Two channel correlation estimation (CCE) schemes exploiting pilots are presented for an OFDM system with a comb-type pilot pattern under the assumption that there exist virtual subcarriers in the OFDM block. Whereas the first scheme is designed based on the conventional regularized-least square (LS) approach, the second scheme is designed by a newly devised technique based on LS. As the second scheme removes the necessity of computing the matrix inverse by making the minimum eigenvalue of the inversed matrix positive, it leads to reduced implementation complexity and improved performance. It is shown by simulation that the proposed CCE schemes substantially enhance the mean equare error and symbol error rate performances of the MMSE based channel estimation by providing more accurate channel correlation information.