The conjecture of Tuinier(J. Colloid Interface Sci. 258 (2003) 45) for the electrical potentials near a cylindrical surface and near a spherical surface under the conditions of symmetric electrolyte and large scaled radius are derived by solving the corresponding Poisson-Boltzmann equation. The surface charge density-surface potential relations for these Surfaces are also derived under the conditions of constant Surface potential. We chow that the level of surface charge density for planar, cylindrical, and spherical surfaces follows the order spherical surface > cylindrical Surface > planar surface. (C) 2004 Elsevier Inc. All rights reserved.