Skilled (SCs) and less-skilled comprehenders (L-SCs) are known for differing in some cognitive and linguistic aspects, including vocabulary knowledge. However, research should more deeply analyze the nature of this vocabulary difference. This study aimed at examining the depth of vocabulary knowledge, lexical-semantic processing and implicit semantic memory in SCs and L-SCs. The participants were 86 eighth-graders from public schools in the south of Brazil, tested with tasks of word definition, semantic judgment, and lexical decision. Results showed that SCs and L-SCs differed significantly in the depth of vocabulary knowledge and lexical-semantic processing but not in the implicit semantic memory. Although it is not clear if L-SCs present lexical-semantic knowledge delay or deficit, the results are more consistent with the hypothesis of a delay. They also suggest that lexical-semantic knowledge and processing may be an important path for intervention with L-SCs.