Despite the fact that the Swiss VET system has been regulated by federal laws since 1930, the 26 cantons that make up the Swiss Confederation enjoy a certain room for maneuver when implementing federal provisions at the regional level. This is reflected in sometimes significant differences between the cantons, particularly with regard to participation in dual VET. Based on a historical reconstruction of the institutionalization process of the Swiss VET system, our contribution first explains the institutional conditions under which cantonal differences are possible; secondly describes their evolution; and finally identifies the main factors which influence their appearance. In more detail, our contribution begins with a reconstruction of the development of VET in Switzerland and in three cantons (ZH, GE, TI) during the decisive period for the Swiss VET system from 1950 to 1970. This reconstruction is based firstly on a historical analysis of sources (laws, messages, statistical data, reports, brochures, press articles, etc.) published from 1880 to the present day, with particular attention to the period 1950–1970. This analysis allows us to reconstruct the process of institutionalization of the field, with emphasis on the constant tension between federal regulation and cantonal autonomy, as well as the statistical evolution of cantonal differences. In a second step, we subject the same set of sources to a discourse analysis allowing us to identify the main arguments accompanying the decision-making process in our three cantons. This latter analysis enables us to show the sometimes-subtle differences between cantonal policies and their respective conceptions of VET.