An apparatus for calculating decision parameters in an IMT-2000 system includes a correlation value calculation unit having a number of correlation value calculators, each of which calculates a correlation value between selected information that is selected at the mini-slot selection unit and one of capable input signals. To selectively operate the correlation value calculators, a ranking determination unit is included to receive and rank the correlation values and to selectively operating the correlation value calculators according to the rank of the correlation values. Accordingly, the power consumption of the correlation value calculators is reduced. And, the decision parameter is selected from the decision parameters previously selected during the divided monitoring section, thereby enabling high-speed cell search.