For a series of monoplanar high-T-c superconductor cuprates a quantitative linear relationship between T-c and the Madelung potential at the Cu site is found. The Madelung potential is calculated using the Ewald summation procedure for a simple ionic model with the crystal structure as the only external input. This correlation opens the possibility to predict T-c of new or modified existing monolayered superconducting cuprates from its crystal structure. The existence of such a linear relationship strongly suggests that the role of the whole crystal structure of the material is crucial and should be explicitly included in the models for high-T-c superconductors. (C) 2003 Elsevier B.V. All rights reserved.