The paper presents the results of a study of equilibrium of a sitting drop from the standpoint of continuum mechanics. It is shown that the connection between internal forces and interfacial tensions is formed by gradients of internal pressures of a medium in interface layers that lead to forming body forces. It was found that the shape of a sitting drop with the contact angle equal Theta_0 = 𝜋/2 is the minimum surface energy state, in which the liquid - solid interface layer is not formed, and the surface energy of the drop takes the minimum value. It was also determined that the thickness of the interface layer varies depending on the values of the contact angle and reaches a maximum value at the complete wetting and complete non-wetting. Finally, the paper examines the impact of external and internal disturbances on the shape of a sitting drop.