Ab initio modelling has left its mark in AS-ALD research already. It provides insights ranging from molecular aspects of inhibitor and precursor chemistry over the crucial question of surface chemistry determining the selectivity of the ALD process to the derivation of mechanisms and design principles. The major workhorse, density functional theory, delivers an efficient and accurate account of the essential chemical reactions in AS-ALD, providing thermodynamic and kinetic signatures. At the current stage, ab initio modelling is mainly used to explain experimental findings and give plausible hypotheses for the observed selectivity and reactivity. In the future, modelling will develop further to obtain predictions and insights, inspiring new experiments in AS-ALD. To this end, several necessary steps are outlined that require developments on the computational side, yet also an even stronger interaction between experimental and computational research in the field.