An experimental and theoretical investigation on the electronic structure of double layer InAs∕GaAs quantum dots (QDs) is presented. In order to evaluate the effects of the quantum coupling between the zero-dimensional states, the spacer separating the two QD layers is varied from 4.5to10nm. The quantitative comparison between experiment and theory is obtained by a previously proposed single band effective masslike model, where the input parameter values are given by a systematic morphological, structural, and spectroscopic investigation of the QD samples. Although the two QDs forming the stacked pairs are not perfectly equal in size, the quantum coupling mechanism is predicted to occur when the spacer is thinner than 8nm and to increase by reducing the spacer thickness. A good agreement between theory and experiment is found for the S, P, and D shell transitions both in single and double QD layers …