In this work a synthesis of the literature data concerning the influence of the so-called “scale” effects on the ferroelectricity of BaTiO₃-based micro- and nanostructured systems is presented. Firstly, some fundamental aspects related to the structure and dielectric and ferroelectric characteristics of barium titanate were summarized. In this context, the structural transitions and the evolution of the electrical properties versus temperature in single crystals and polycrystalline ceramics were discussed comparatively. Afterwards, some particularities of the ferroelectric characteristics appearing at nanometer scale in systems as nanocrystalline ceramics, thin films and nanopowders were revealed. The role of the processing route and processing parameters on the value of critical grain size for ceramics, critical thickness and critical crystallite size for thin films and critical particle size for powders was also pointed out. Below these critical size values the ferroelectricity in barium titanate is suppressed by the ferroelectric – superparaelectric phase transition.