The answer to the question to what extent the study of law participates in the process of law creation is a difficult one. It seems that legal doctrine achieves far more as far as its influence on law application is concerned. In this scope, the influence of research is more visible. This influence is reflected in frequent references to the stand of research in the rulings of the bodies applying law, in particular courts situated at the top of the judiciary hierarchy, as well as in using the expertise carried out by lawyers who are researchers in the field of law interpretation. Nonetheless, in the range of research which is under discussion, concerning law creation and changes in the area of law, the study of law and legal doctrine have much to say. This influence can be observed both in general and in more particular issues. This phenomenon is multidimensional and in this draft it is difficult to analyse all its aspects. In its basic dimension, concerning the rules of law making process, these are issues in the theory of law. What is being discussed are general conditions and rules of the dynamics of law. One attempts to formulate generalizations and regularities as well as present alternative models of law making process. In the broader scope, where direct and indirect influences are discussed, additional phenomena can be analysed, namely findings in sociology, law and legal policy. In social and political practice some complicated subjective relations manifested in serving multiple social functions by the representatives of the doctrine can be the subject of analysis. The lawyers who are devoted to academic research, do not shun legal practice, often connecting it with political or administrative functions. Potentially, then, they can favour their own or borrowed academic conceptions in the practice of law creation. Finally, it is the outcome of a particular kind of legal culture as well as the position and authority attributed by the system to researchers. The influence of the doctrine on law making process in its particular dimension is manifested in presenting particular solutions, specific legal contents and the postulate of introducing them to currently binding law. What can determine the effectiveness of de lege ferenda postulates? De lege ferenda postulates of legal doctrine can be treated in this process as a kind of impulse. The question then arises who should the postulates of the doctrine formulated in the scope of changes in law be addressed to. Can reasoning be applied at all and if it can, then the question occurs what kind. It can be assumed that particular kinds of reasoning can be combined with the hereunder mentioned areas. By means of discussion, or rather signalling certain types of reasoning, I aim at pointing at the fact that their utilization constitutes the accomplishment of de lege ferenda postulates. This effectiveness is obviously a potential one, depending not only on the importance of the argument but also on whether and to what extent it is feasible to reach a particular decision making bodies with these arguments.