This study examined whether Greek (Gr) and Japanese (J) learners of English perceive the Southern British English (SBE) vowels in the same way. Both languages have five vowel qualities in their vowel inventories but only Japanese has short/long versions of each quality. Experiment 1 assessed the perceived relationship between the eleven SBE vowels (in /b_b/ and /b_p/ contexts) and the L2 vowel categories for both language groups via a cross-language mapping test. Experiment 2 assessed the discrimination of several SBE vowel contrasts by the same participants via a categorical oddity discrimination test. Differences between the two L2 groups in both experiments support the view that L2 perception cannot be predicted by an abstract phonological description of the two vowel systems. L1 experience with duration helps perception of some L2 contrasts; Gr listeners nonetheless seem to be able to use duration to some extent.