In the framework of G-cone metric spaces introduced by I. Beg, M. Abbas and T. Nazir , Generalized cone metric spaces, J. Nonlinear Sci. Appl. 3 (1) (2010), we prove several fixed point theorems for mappings satisfying T-Kannan, respectively T-Chaterjea contractive conditions, as well as for weakly commuting pair of mappings satisfying contractive conditions. Our results extend and improve similar results that are known in cone metric spaces.