The numerical approach for determination of influence of deformation of the gas bubble (radius 0.74 mm) on added mass coefficient in (i) steady-state conditions and (ii) during approach to the horizontal wall, is proposed. It is shown that the bubble deformation can be tuned numerically (within the range 1.06 - 1.88) via proper variations of the Laplace pressure, without changing the bubble radius. Influence of the bubble deformation on its motion parameters is discussed and compared to theoretical predictions regarding the bubble drag coefficient and Reynolds number. Moreover, the approach allowing determination of the added mass of rising bubble, on the basis of variations in fluid kinetic energy, is described. It is shown that calculated added mass variations strongly depends on the interplay between (i) the bubble deformation ratio and (ii) its rising velocity. This effect is especially important for added mass of a gas bubble approaching a solid wall, because it can affect the kinetics of drainage of the separating liquid film formed under dynamic conditions, when Re >> 1.