In this paper are presented the results obtained after of evaluating three techniques of blind detection of spectrum holes used in Cognitive Radio (CR). The techniques evaluated correspond to the general technique of detection of energy levels, the method LAD BASED and the technique based on forward methods. The operation of these techniques was tested in simulation scenarios of a telecommunications system using Matlab®, on a Gaussian channel (AWGN) and a channel with Rayleigh fast fading. The analysis of performance obtained by each one of these techniques, was based in the probabilities of the binary hypothesis of the theory of signal detection (TSD). In this theory the probabilities of detection (PD) and false alarm (PFA) are the variables to be evaluated.