Optical properties of Cu₂O-metal core-shell nanostructures containing Rydberg excitons are examined. Calculations of electron and hole eigenfunctions and eigenenergies are used to calculate exciton energy and its dependence on system geometry and dimensionality. The limits of very small and very large structures are discussed, making the results applicable to low principal quantum number excitons as well as to Rydberg states. The Real Density Matrix Approach method is used to calculate the optical properties of the studied systems.