English as a foreign language (EFL) is a global issue that extends to thousands of learners worldwide who share a similar classroom situation. However, researchers have often considered learners to have homogeneous linguistic profiles, overlooking the fact that EFL classrooms in primary and secondary education include learners with different linguistic profiles. Despite the fact that immigrant and non-immigrant students meet every day in classrooms, little is known about the EFL performance of the former compared to the latter. This paper addresses this reality, and explores the vocabulary performance of immigrant students, learners of English as an L3, compared to learners of English as an L2 who had the same course level and were from the same community. The research questions were twofold: (1) to ascertain whether there were quantitative differences between L2 and L3 English learners in terms of the number of words produced by each group; and (2) to ascertain whether there were qualitative differences in the words produced by the L3 and L2 groups with regard to (a) the most and least productive prompts for each group, and (b) the number of infrequent words appearing in the production of each group. The sample consisted of 14 bilingual students who were learners of English as an L3 and 14 monolingual learners of English as an L2, respectively, who were in the twelfth year of Spanish secondary education (age 17-18 years old). The data collection instrument was a lexical availability task consisting of six prompts. The data were lemmatized, coded and analysed by means of WordSmith Tools and the VocabProfile programme. The results indicated that the L2 group produced a greater number of words and a higher percentage of infrequent words in the most productive prompt.