Abstract A study of the excitonic states in artificial molecules set up of two vertically coupled double quantum dots is presented. The electron and hole eigenstates are calculated for the quantum dot molecule. In particular, the coupling effect of the barrier and the consequent tunneling is analyzed following the evolution of the absorption spectra as function of the distance between the two dots. On the other hand, the role of the Coulomb correlation between the confined particles is also studied. We present results of relevant interactions in these systems and discuss how the optical properties of double quantum dots are affected by the interdot coupling, by the geometry of the dots and by an applied electric field. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)