In connection with the development of nuclear energy in Poland, issues of nuclear law are gaining in importance. It is becoming increasingly relevant both for legal practitioners as an area of economic activity and for academics as an emerging, new subject of legal research. While most of the emerging studies in Poland understandably focus on the present, there is a lack of references in the academic discourse to the origins of the development of this particular area of law. In an attempt to fill this gap, this article looks back to the Second Polish Republic, a period when a new development in science and technology - ionising radiation - began to be used on a wider scale in medicine and industry in Poland. The purpose of the article is to examine whether and to what extent there were generally binding regulations on the use of ionising radiation and nuclear energy in Poland at that time. The article discusses the totality of Polish legislation in this field at that time. In particular, it discusses the first regulations in the field of radiation protection, as well as in areas such as the use of X-ray machines in health care, labour and social insurance law, customs law, mining law and the promotion of nuclear energy. Although the legislation at that time was sparse and did not form a coherent system, it provided a kind of starting point for more extensive state legislative activity in the 1950s and 1960s.