In [Stud. Cercet. Ştiinţ. Ser. Mat. Univ. Bacău No. 7 (1997), 127–133 (1999); MR1721711], V. Popa initiated the study of fixed points for mappings satisfying implicit relations as a way to unify and generalize various contractive conditions. Later on, many papers were published extending this approach to different metric settings. In the paper under review, the authors prove a result of such type for two mappings defined on two generalized metric spaces, called G-metric spaces and introduced by Z. Mustafa and B. Sims [J. Nonlinear Convex Anal. 7 (2006), no. 2, 289–297; MR2254125 (2007f:54049)].