The article discusses the legal nature of a Sejm resolution to appoint an investigative committee. This problem appeared in the context of the judgment of the Constitutional Tribunal of 22 September 2006 (Act Call No. 4/06). In that judgment the Tribunal ascribed a normative meaning to a Sejm resolution on the appointment of an investigative committee to the extent in which it indicates the subject matter of the activity of that organ. Such committee is an instrument of oversight. In the light of Constitution of 1997, it is justified to claim that the exercise of such function is conferred, in principle, exclusively on the Sejm, whereas the oversight competence of the Senate in relation to a Sejm investigative committee is limited to participation in the proceedings aimed at adoption of a statute (act of parliament) specifying the rules of procedure for that body. The Sejm appoints an investigative committee by means of a resolution. However, resolutions of the Sejmu does not form a uniform category. Most of them take the form of acts of application of law (Poland's Constitution), but a large part of them have no binding nature. Some of them will belong to the sphere of making universally binding law or internally binding law. Ascertaining the nature of the provisions of the resolution opens the way to the examination of rightness of the used form of regulation.. Not always the normative character of resolutions implies from their nature. Only certain resolutions, and sometimes – to a limited extent, have the nature of normative acts. So, an analysis of particular provisions of a Sejm resolution is vital for declaring its normative character. The presence of any normative content justifies the subjecting of the act to the review of constitutionality or legality, particularly when the protection of the rights and freedoms of the person and citizen is at stake. In such situations, the Constitutional Tribunal applies a peculiar presumption of normative nature of legal acts. A resolution establishing an investigative committee of the Sejm is not tantamount to a resolution on appointment of its members. Moreover, the resolution establishing a committee is not a uniform act. Firstly, it creates the committee. In this part, it is an individual act. Secondly, it specifies the subject matter of the committee work, which should be recognised as lawmaking activity of universally binding nature. This resolution may also specify detailed principles of operation of the committee and the time limit for submission of a report by it. In that part, the resolution has rather an internally binding nature and, therefore, it should be counted among acts of lawmaking. Due to the binding nature of some provisions in relation to extra-parliamentary bodies, it may be recognized as a normative act of universally binding force.