The purpose of the research was to recognise the nature of the above mentioned solutions, to identify their common features and the differences between them. It was assumed that based on the two determinants of the occurrence of competition in the railway sector – the determinant of access to the market and the determinant of the unprofitability of a large part of transport services – it is possible to construct two basic models of pro-competitive legal solutions in the area of passenger railway transport services – “competition on the market” model and “competition for the market” model. In case of the “competition on the market” model the aim of the law is to ensure competition between railway undertakings at the stage of performing transport services. In case of the “competition for the market” model the railway transport services are entrusted through a competitive and non-discriminatory tender procedure. In such a situation competition occurs at the stage of the selection of the service provider, however it is excluded at the stage of providing the transport services. This doctoral thesis has been written under the supervision of Professor Zbigniew Cieślak. Professor Zbigniew Cieślak also had a great influence on the preparation of the above mentioned book. He used to say that scientific research should be treated as some kind of an adventure. Almost ten years after the book was published, it was decided to go back to that “adventure” and investigate whether the findings presented in the book are still valid.