The perfectnes of crime and the forms of crime difficult their investigation. In order to protect humans and citizens rights and freedoms the state is obligated to apply even such methods, that restrict criminals rights. The subject of this work is ambiguously considered application one of these forms, to be exactly, the form of application secret agents during the investigation in criminal procedure. The participation of secret agents investigating crimes, the results of this investigation are looked over the prism how these results could be used in criminal procedure as the poof of quilt. Considering this question is settled that legal application of secret agents and the conception of proof allow to use this form of investigation and their results as the proof in criminal procedure. It has to be noted, that secret agents as the form of investigation is restricted and allowed in very particular cases, if secret agents don’t go beyond law and settled sanction by court. In conclusion it can be also mentioned, that in this work were identified the problems of regulation of applying this criminal – procedural investigation method, that can cause the slip of efficiency of the investigation and its results.