  Masses for $\{Q\bar{q}\}\{\bar{Q}^{(')}q\}$ molecular states are
systematically studied in QCD sum rules. The interpolating currents
representing the related molecular states are proposed. Technically,
contributions of the operators up to dimension six are included in operator
product expansion (OPE). Mass spectra for molecular states with
$\{Q\bar{q}\}\{\bar{Q}^{(')}q\}$ configurations are obtained.
