The study examines the place of behavioural economics in the structure of economic science and the practice of state regulating. The thesis that neoclassicism is an appropriate normative approach for analysing human behaviour is defended but the comparative advantages are on the side of behavioural economics in the answers of escriptive, diagnostic, prognostic and perspective questions. It tracks the historical roots, the ideas of behavioural economics for the limited rationality, will and egoism are presented in short as well as the contribution of behavioural approach to the state intervention’s ideology and practice. The libertarian paternalism idea and its role for the transformation of “state of wealth” into the gaining clearer and clearer outlines “new paternalistic state” are presented.