Two new glycoluril derivatives, namely diethyl 6-ethyl-1,4-dioxo-1,2,2a,3,4,6,7,7b-octahydro- 5H-2,3,4a, 6,7a-pentaazacyclopenta[cd] indene-2a,7b-dicarboxylate, C14H21N5O6, (I), and 6-ethyl-2a, 7b-diphenyl-1,2,2a, 3,4,6,7,7b-octahydro-5H-2,3,4a,6,7a-pentaazacyclopenta[cd] indene-1,4-dione, C20H21N5O2, (II), both bearing two free syn-urea NH groups and two ureidyl C=O groups, assemble the same one-dimensional chains in the solid state running parallel to the [010] direction via N-H center dot center dot center dot O hydrogen bonds. Furthermore, the chains of (I) are linked together into two-dimensional networks via C-H center dot center dot center dot O hydrogen bonds.