To verify and compare the performance of children and adolescents with Specific Language Impairment (SLI) and Autism Spectrum Disorder (ASD) using a formal, standardized test that assesses language competence, more specifically comprehension of ambiguity. The sample comprised 19 individuals aged 6 to 14 years, of both genders, divided into two groups: ASD Group (9) and SLI Group (10). Participants were assessed using the Test of Language Competence - TLC; Ambiguous Sentences subtest (Wiig, Secord, 1989). Analysis included the comparison of the total scores in both groups. We found significant difference between the groups, with better performance of the SLI Group compared with that of the ASD Group. It was possible to analyze and compare the performance of both groups in a metalinguistic activity. We observed better performance of the SLI group compared with that of the ASD Group in the interpretation of ambiguous information.