Hiking trails are a basic type of tourist infrastructure, which, on the one hand, make areas available for tourist traffic, and on the other hand, can contribute to the protection of the natural environment (if they are well designed and maintained). Owing to the variety of performed functions, their designation is determined by several factors: natural, technical, economic, social. Networks of trails change constantly. The aim of this article is to determine exactly what factors influence transformations within the hiking trail networks and what is their significance. To this end, three study areas in the Sudetes were analysed: one on the Polish side of the Sudetes–the Table (Stołowe) Mountains, and two on the Czech side–the rock town near the village of Sloup v Čechách and the central part of Zlatohorská vrchovina. An analysis of changes in the shape of the networks over time was carried out, as well as surveys of institutions that were responsible for or influenced these transformations. These areas are characterised by a significant level of changes in the trail network. Among the factors influencing these changes, the tourist attractiveness of the area, the resilience of the environment, the intensity of tourism traffic, the environmental transformations associated with it, the history of tourism development and land ownership changes should be considered the most important. At each stage of forming networks, the key factor should be tourists’ needs, including the desire to escape the urbanised environment. For this reason, trails should avoid roads with artificial (hard) surfaces and heavy automobile traffic.