Although a large body of literature exists on age-related differences in second language acquisition, few studies are available on older second language learners. Our aim is to analyse the effect of previous foreign language contact on the acquisition of receptive and productive English vocabulary by senior learners in the early stages of acquisition. Data were gathered from 18 senior L2 English learners divided into a group of true begnones (n=7) and a group of false begnones (n=11). Four tests were administered: (i) a 1,000 receptive word test (Nation, 1993), (ii) the 2,000 word frequency band from the receptive version of the Vocabulary Levels Test (VLT) (Schmitt, Schmitt and Clapham, 2001), (iii) a lexical availability test based on Carcedo-González (1998), and (iv) a reading comprehension test taken the Key English Test 1 (C.U.P., 2003).The results confirm that false begnones either significantly/tendentiously outperform true begnones in all the administered tasks, supporting previous research findings (Fukai, 2000; Watt, 1997). The lexical availability test is found to be positively correlated with the receptive vocabulary tests, which indicates that there is a direct relationship between the passive and the active knowledge of L2 vocabulary. Besides, learners’ productions under the different prompts in the lexical availability task are significantly correlated too, suggesting that productive vocabulary size pervades different lexical fields. Additionally, a comparison of our results to research carried out with primary school children in Spain in formal contexts reveals that begnones trespass similar developmental stages in the acquisition of vocabulary irrespective of age.