The dependences of the fundamental transition on the quantum dot size obtained experimentally at various temperatures using different measuring methods are analyzed and compared. A simple analytical relationship for approximation of these dependences is proposed. The possibility to extrapolate the results for the case of arbitrary temperature is discussed. Semiconductor low-dimensional systems, in particular semiconductor quantum dots, attract a considerable interest due to the substantial size dependence of the energy of quantum transitions in them. This feature is promising for development of absorption and luminescent materials necessary for solving a wide range of applied problems from optoelectronic imaging and data transfer devices to biological fluorescence labels [1, 2].