  This paper is devoted to the study of leading twist light cone wave function
of $\eta_c$ meson. The moments of this wave function have been calculated
within three approaches: potential models, nonrelativistic QCD and QCD sum
rules. Using the results obtained within these approaches the model for the
light cone wave function of leading twist has been proposed. Being scale
dependent light cone wave function has very interesting properties at scales
$\mu> m_c$: improvement of the accuracy of the model, appearance of
relativistic tail and violation of nonrelativistic QCD velocity scaling rules.
The last two properties are the properties of real leading twist light cone
wave function of $\eta_c$ meson.
