This study aims at comparison of buckling loads of masonry slender columns having rectangular and circular cross-section subjected to their own weight and eccentric vertical top load. It has been assumed that the material of the columns is a homogeneous continuum which has no tensile strength and, linear-elastic in compression. For the practical determination of the buckling loads, an effective calculation method existing in the literature has been adopted. For sample square and circular columns, buckling loads have been obtained and the effect of cross-section shape discussed. Finite element model for one of the square columns has been created with the Abaqus program, the buckling load has been determined and compared with the result of the present study's method. It has been seen that there is a good agreement between the results. Variation of buckling loads of the considered columns depending on the load eccentricity have been determined. Moreover, analytical expressions have been obtained for the variation of buckling loads of the square and circular columns depending on the vertical load eccentricity.