Steel, spherical shells subjected to an external pressure are exposed to the loss of stability and such a phenomenon determines the global resistance of such shells. Unavoidable, geometric imperfections present is this class of shells affect significantly global resistance of shells. The imperfection form corresponding to the first and second buckling modes, analysed in previous works of authors, do not cover all possible and observed in reality imperfection modes. The specification and comparison of other imperfections encountered in practice will allow to identify the most adverse ones. Additionally to the imperfection forms also their amplitudes were analysed. Consequently the ranges in which considered imperfection form is in fact the most adverse were determined. On the basis of this knowledge, the designer can choose the most adverse imperfection mode for given quality fabrication class of the shell.