The interaction between two identical, thin, disks of finite thickness is investigated theoretically. We show that the thickness of a disk may play a significant role in the estimation of the electrical and the van der Waals interaction energies between two disks. These interaction energies depend largely on the surface conditions oi a disk, its thickness and the relative orientation between two disks. If the basal plane of a disk is negatively charged, and its edge face positively charged, then for a fixed total amount of charge charge on the edge face the thicker the disk, the greater the absolute electrical interaction energy. This implies that neglecting the thickness of a disk will underestimate the absolute electrical interaction energy. If the masses of disks and the separation distance between them are fixed, the thinner the disks, the greater the absolute van der Waals interaction energy. The results for the total interaction energy between two disks reveal that neglecting the thickness of a disk may result in not only a quantitative deviation but also a qualitative deviation. Lu general, the effect of the thickness of a disk should be considered if two disks are closer than two Debye lengths.