AbstractVapor‐deposited thin films grown under conditions of oblique incidence commonly develop a microstructure of columns, inclined at an angle β relative to the substrate normal, which differs from the angle of incidence α. Here it is shown that the functional relation β(α) is universally linked to the dependence of the film density ρ on the angle of incidence, through the equation tan β=tan α + ρ−1(dρ/dα). The theory is supported by an analysis of published numerical data obtained from simulations of ballistic deposition of disk