The Grammatical Structures Comprehension Test (CEG) was used to analyze grammatical comprehension problems in native Spanish-speaking children with Specific Language Impairment (SLI). The test is divided into 20 blocks containing the most common grammatical structures in Spanish. Our objective was to establish whether the CEG was sensitive in detecting these problems and whether there were differential patterns in grammatical comprehension between children with SLI (14 participants) and two control groups: a chronological control group (CC) with 14 participants and a linguistic control group (LC) also with 14 participants. We found significant differences between the SLI group and the chronological control participants (Box’s M = 63.080, F = 1, 159, p = .238), with a correct classification rate of 85.7 % in the discriminant function analysis. These differences did not occur in all the blocks, in which we identified a range of different performance patterns that varied according to the structures being analyzed. This work helps to clarify certain questions about grammatical comprehension in children with SLI and contributes to the debate on delay vs. “delay within the delay”.